(P5: G818E/L541P+A1038V

Through a meta-analysis of published literature38,39, we also found that individuals with inherited retinal disease caused by recessive ABCA4 deficiency (Stargardt disease or cone rod dystrophy) are likely to have ASO-amenable variants in similar proportions (Supplementary Note 7 and Supplementary Tables 15 and 16), leading us to suggest that around 15% is a reasonable first estimate for other recessive genetic conditions.

Patient 2 (P2), previously described in a large IRD cohort study [1], is also of Somali origin and was seen in the retina clinic at the University of Iowa at age 11

P12‡20MG1961EG1961E/P68L

MD-0084ABCA447c.6410G>Ap.Cys2137Tyr47c.6410G>Ap.Cys2137Tyr7YesABCR400 + dHPLC + HRM + MLPAValverde et al. 2006 (6); Aguirre-Lamban et al. 2010 (16)

Of the 266 arSTGD chromosomes studied, mutations were identified in 161, resulting in a detection rate for the genotyping microarray of 60.5%: two mutant alleles were found in 64/133 patients (48.1%), whereas in 33/133 cases (24.8%) only one allele could be identified. A total of 56 different sequence variants related to the disease were identified, including missense (42), nonsense (four) frameshift (five) and splicing (five) mutations. Furthermore, combinations of variants acting in cis (complex alleles; six double alleles, one triple allele) were also found. Of this spectrum of substitutions, the p.Arg1129Leu (c.3386G>T) allele accounted for 26% of the disease-associated alleles (fig 2). Considering the percentage represented by this variant in patients (26%) and the obtained mutation detection rate (60.5%), this change would represent the 15.7% of all the potential arSTGD associated alleles.

MD-0560 STGD1 23 c.3386G>T p.(Arg1129Leu) 47 c.6410G>A p.(Cys2137Tyr) Yes 16 20 - 53y Normal 0.1/0.1 Riveiro-Alvarez et al.,2013

MD-0247 STGD1 23 c.3386G>T p.(Arg1129Leu) 47 c.6410G>A p.(Cys2137Tyr) Yes 12 12 - 22y Cone-pattern 0.05/0.1 Riveiro-Alvarez et al.,2013

47 c.6410G>A p.(Cys2137Tyr) Aguirre-Lamban (2008) Hum Genet 123 547 8 missens

Stargardt disease (STGD) and fundus flavimaculatus are infrequent autosomal recessive conditions characterized by a juvenile macular dystrophy and variable degrees of peripheral retinal changes. Linkage analysis performed in 47 STGD/fundus flavimaculatus families demonstrated significant linkage to 13 polymorphic DNA markers on chromosome 1p. The maximum combined two-point lod score was 32.7 (maximum recombination fraction [phi max] = .006) with the polymorphic marker D1S188. Our data demonstrate that STGD and fundus flavimaculatus are the same disorder clinically and genetically and provide further evidence for genetic homogeneity of this phenotype. Analysis of recombination events on disease chromosomes placed the STGD gene within a 4-cM interval between markers D1S435 and D1S236. A physical map was constructed of a YAC contig flanking STGD, from markers D1S500 to D1S495, and includes the critical interval delineated by historical recombinants. This contig spans approximately 31 cM, with one gap (3-5 cM) that is outside the 4-cM critical region. Localization of STGD to a single YAC contig will facilitate its positional cloning.

This work reported presence of 22 alterations, including two changes not found in other populations, c.2T>C (p.Met1Thr) and c.4036_4037delAC (p.Thr1346fs), and two novel disease associated variants, c.400C>T (p.Gln134X) and c.4720G>T (p.Glu1574X).

Patients and Methods The protocol of the study adhered to the provisions of the Declaration of Helsinki. After informed consent was obtained, blood samples were taken and molecular analysis on the ABCA4 gene was performed as described by Maugeri et al. 14 The charts of patients with ABCA4 mutations who originally had received diagnoses of isolated or autosomal recessive CRD were reviewed. All patients originated from the University Medical Centre Nijmegen (Nijmegen, The Netherlands) and the University of Heidelberg (Heidelberg, Germany). In this study the diagnosis of CRD was based on the following criteria: initial symptoms of blurred central vision without a history of night blindness, impairment of color vision, and fundoscopic evidence of maculopathy without or with mild peripheral retinopathy. 3 4 5 7 8 In patients with recordable ERGs a cone–rod pattern of degeneration had to be present (i.e., the photopic b-wave impairment had to be greater than or equal to the scotopic b-wave amplitude impairment). Patients 9250 and 13163, who had nonrecordable ERGs, were included because their histories and clinical features were similar to those of other patients with cone–rod degeneration and they were believed to represent advanced cases of CRD. In addition to an ophthalmic examination, Goldmann kinetic perimetry routinely was performed using III-4-e and I-4-e isopters. Color vision was tested with the Ishihara and Panel D15 tests, except in patients 9369, 9378, and 10125, who were tested under conditions described earlier. 18 Because these patients were examined in two different clinics and ERGs were recorded over a long period, the methods, instrumentation, and analysis techniques of the electroretinography varied. The ERGs in patients 9369, 9378, 10125, and 11872 were performed as described by Thijssen et al. 19 The ERG method used in patients 9370, 9553, 9633, and 13163 was described by Alexandridis and Krastel. 20 The ERGs of the remaining patients (9250, 9371, and 9650) are of a more recent date and were performed according to International Society for Clinical Electrophysiology of Vision (ISCEV) standards. 21 Fundus photographs were taken in most patients and some of the patients (9650, 9369, 9378, and 10125) also underwent fluorescein angiography.  Results The characteristics of 12 patients with ABCA4-associated retinal dystrophy resembling CRD are summarized in Table 1 . Most did not have affected family members, and therefore their retinal dystrophies could not be classified as autosomal dominant, autosomal recessive or X-linked. Four patients reported a brother or sister with subnormal vision. In view of the reputedly normal visual acuity of the parents and the molecular defects, the inheritance pattern of the gene defects in these patients (individuals 9303, 9369, 9553, and 13163) was classified as autosomal recessive.  The visual acuity of the patients did not exceed 20/200 and, on average, was much lower. With the exception of patient 9553, the age of onset was at or before the age of 12, and in each of the patients, blurred vision was the initial symptom. Night blindness did not occur except in patients 9378 and 10125, in the final stages of retinal degeneration. Evidence of maculopathy in the form of bull’s eye maculopathy or pigmentary changes was present in all the patients reported in this study (Fig. 1A) . The functional equivalent of the mainly centrally located retinal disease was a central scotoma, varying from 8° to more than 40°. In all but one patient, the scotoma was absolute. Only in patient 9378 was the central scotoma relative and surrounded by absolute scotomas. Fundoscopic evidence of early peripheral involvement of the retina was mild, and only in the later stages of the disease did peripheral changes characteristic of RP, such as narrowing of retinal vessels and bone spicula, occur in patients 9369 (Fig. 1B) and 10125. Similarly, mild constriction of the visual fields occurred only in two patients (9650 and 10125) and only in the advanced state. Color vision was tested in 10 patients. Six demonstrated a red–green defect, and in two of these (patients 11872 and 10125), it was accompanied by a blue-yellow defect. In the remaining four patients, color vision was so severely disturbed that the exact type of impairment could not be assessed.  The ERG recordings demonstrated degeneration of both rods and cones. When ERG responses could be elicited, the cones appeared to be affected as much as the rod photoreceptors and, in most of the patients, even more severely. The ERG responses in five patients progressively deteriorated until no photopic and scotopic responses could be recorded. In these patients, with exception of patients 9250 and 13163, ERG recordings of an earlier date were used in Table 1 . This applies to patient 9369, in whom an ERG was recorded at age 12 (all ERG responses had been nondetectable since the age of 21), patient 9378 at age 33 (all ERG responses at age 46 were nondetectable), and patient 10125 at age 8 (in 1998, at age 28, the ERG responses were no longer detectable). Recent ERG findings were not available for patients 9650 and 9371. Their ERGs were recorded in 1989 and 1985, respectively. The remaining ERG data were derived from ERG recordings performed in the past 4 years. Of patient 9371 only the ERG data in the left eye were available.  Two patients warrant a more detailed description, due to the unusual course of their retinal dystrophies. Patient 9378, at the age of 12, had blurred vision with fundoscopic evidence of irregular chorioretinal atrophy in the posterior pole. At that time, there were no peripheral abnormalities on ophthalmoscopy, and there was no history of night blindness. The ERG demonstrated an equal reduction of both cone- and rod-mediated responses. Later in life, however, fundoscopic changes developed that were characteristic of RP, and the patient reported a decrease in night vision. With fluorescein angiography partly confluent patches of chorioretinal atrophy were visible (Fig. 1C) .  The clinical picture of patient 10125 differed from that of the other patients, despite the mutation in the ABCA4 gene. Initially, disease in this patient was diagnosed as STGD because of the bull’s eye maculopathy, the granular pigment alterations in the macular area, and the pisciform flecks surrounding the posterior pole. At age 8 his visual acuity had decreased to 20/200 in both eyes. When he was referred to our clinic in 1998 at the age of 28, peripheral degeneration in the form of narrow retinal vessels and deposition of peripheral bone spicula had developed, in addition to the earlier described disease of the central retina. A fluorescein angiogram showed typical findings: a central small hypofluorescent spot enclosed by an ellipsoid—a markedly hyperfluorescent area that in turn was surrounded by hyperfluorescent dots against a dark background, most likely caused by obscuration of choroidal background fluorescence (Fig. 1D) . Early ERG recordings were not available, and the ERG tracings recorded at age 28 represent the final stage of the degenerative process, with absence of both cone and rod responses. This retinal dystrophy seemed to have evolved from STGD into more widespread retinal degeneration, resulting in loss of function of both rods and cones.  Discussion Progressive CRD is a clinically heterogeneous retinal disorder, but typical findings include reduced visual acuity, impairment of the central visual field, color vision deficits, and fundoscopic evidence of maculopathy, with no or few midperipheral retinal pigment deposits. 3 4 7 8 There is some dispute about typical ERG findings in CRD. Some state that the diagnosis of CRD must be based on the reduction or absence of cone responses in the presence of quantitatively less reduction in rod responses, whereas others state that an equal impairment of both photoreceptor systems, if accompanied by the characteristic features, suffices to justify the diagnosis of CRD. 3 7 8 22 Several propositions have been made in the past to classify cone–rod disorders. Some classification systems have focused on individual case reports and were based on nosologic aspects; others have made a distinction according to the various patterns of inheritance. 3 6 23 24 In recent studies, Szlyk et al. 7 and Yagasaki et al. 8 made use of full-field ERGs, dark adaptometry, and modified perimetric techniques to identify functionally distinct subtypes of CRD. Finally, over the past few years, a molecular genetic classification of CRD has emerged.  At the moment, four genes and three loci have been implicated in autosomal dominant CRD, whereas one X-linked locus has been described. 25 26 27 28 29 30 31 32 Thus far, two loci and one gene (ABCA4) have been associated with autosomal recessive CRD. 12 33 34 The genetic heterogeneity seen in CRD is matched by the range of the clinical findings attributed by various investigators to this type of retinal dystrophy.  Whatever the classification system used, some patients display retinal disorders that cannot be classified satisfactorily. Often, these retinal degenerations involve overlapping features. Krill et al. 5 reported that 9 of 45 patients with cone degenerations showed typical features associated with fundus flavimaculatus. Heckenlively 2 described 76 patients with cone–rod patterns on the ERG in whom retinal disease otherwise met the standard definition of RP (progressive peripheral visual field loss with ring scotoma). Alternatively, as seen in patient 10125 in this study, patients with STGD have been described who had progressive peripheral retinal degeneration with severe abnormalities in the ERG and electro-oculogram (EOG) later in life—a condition that has been described by Fishman 4 as secondary progressive cone–rod dysfunction.  The association of CRD and a dark choroid has also been described previously. 35 36 The atypical pattern of retinal degeneration with confluent patches of chorioretinal atrophy in patient 9378 resembles that in another previously described unrelated patient with CRD-like disease caused by mutations in ABCA4. 37 In the molecular genetic study by Maugeri et al., 14 in which 11 of the 12 patients with autosomal recessive CRD described in this study were analyzed, ABCA4 mutations were found in 13 of 20 unrelated patients, strongly suggesting that ABCA4 mutations are the major cause of this disorder. If this is true, the genetic heterogeneity in autosomal recessive CRD, compared with, for example, classic RP, is surprisingly low. Because autosomal recessive inheritance is believed to be the most frequent mode of inheritance of monogenic chorioretinal disorders, it is very possible that a large fraction of the patients with CRD who have been clinically studied previously carry ABCA4 mutations. In that case, the explanation for the high variability of the clinical findings in autosomal recessive CRD would not be genetic heterogeneity but rather the genotype–phenotype model for ABCA4. According to this model, there is an inverse relationship between the presumed residual ABCA4 function as an N-retinylidene-PE flippase and the severity of the disorder. 12 37 38 As a consequence, a continuum of phenotypes is to be expected, ranging from STGD to CRD to RP. Although this is probably a simplified representation of reality and needs corroboration by detailed biochemical studies of individual mutations, as described previously, this model explains why mutations in the ABCA4 gene could give rise to phenotypes that do not satisfy the standard classification of retinal dystrophies. 39   Two patients in this study may reflect borderline CRD phenotypes. Patient 9553 carries a combination of a mild (2588G>C) and severe ABCA4 mutation, which, according to the genotype–phenotype model described earlier, should be associated with STGD. We have previously discussed that most likely, one of the pathologic mutations has not yet been identified in this patient. 14 However, the age of onset in this patient (25 years) is relatively high, and although other features such as visual acuity, perimetry, and ERG findings are typical of CRD, this may indicate a relatively mild subtype. Another more convincing example of blending of ABCA4-associated phenotypes is patient 10125. The molecular findings in this patient have not yet been described elsewhere. He carries a severe splice site mutation (IVS30+1G→T) in combination with a nucleotide change leading to a stop codon at Gln1029. A patient with RP who was homozygous for the IVS30+1G→T mutation has been described, 12 whereas the Q1029X mutation has not been described. Both mutations can be considered to be null alleles. According to the proposed ABCA4 model, the clinical phenotype in patient 10125 should be RP. Instead, this patient exhibits a typical retinal dystrophy, which gradually progresses from STGD to a more widespread degeneration of photoreceptors in a cone–rod pattern later in life. At present, both rod and cone ERG responses are not detectable, indicative of a final stage similar to that in many patients with RP. Functional studies are necessary to clarify whether these specific ABCA4 mutations are responsible for the particular progression of the retinal degeneration in this patient, or whether other as yet unknown modifying factors play a role.  In this study we have described 12 unrelated patients with retinal dystrophy resembling CRD caused by mutations in the ABCA4 gene. In a previous study we described the ophthalmic features in five siblings with CRD-like retinal dystrophy who were carrying ABCA4 mutations. 37 From the clinical data of these patients and previous molecular studies in patients with autosomal recessive CRD, two important conclusions can be drawn. 12 14 First, the genetic basis of autosomal recessive CRD is less heterogeneous than was thought, based on the variability in clinical features, because mutations in the ABCA4 gene seems to be the major pathologic cause. Second, given the wide clinical spectrum of CRD-like phenotypes associated with ABCA4 mutations, detailed clinical subclassifications are difficult and may not be very useful.   Supported by the British Retinitis Pigmentosa Society, the Rotterdamse Vereniging Blindenbelangen, the Algemene Nederlandse Vereniging ter Voorkoming van Blindheid, the Stichting Blindenhulp, the Stichting de Drie Lichten, the Gelderse Blindenvereniging and the Landelijke Stichting voor Blinden en Slechtzienden and the Stichting voor Ooglijders.  Submitted for publication June 15, 2001; revised December 21, 2001; accepted January 2, 2002.  Commercial relationships policy: N.  The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.  Corresponding author: B. Jeroen Klevering, Department of Ophthalmology, University Medical Centre Nijmegen, PO Box 9101, 6500 HB, Nijmegen, The Netherlands; b.klevering@ohk.azn.nl. Table 1. View Table Patients with Cone–Rod Degeneration and ABCA4 MutationsTable 1. Patients with Cone–Rod Degeneration and ABCA4 Mutations Patient Sex Current Age (ys) ABCA4 Mutations* Visual Acuity Age of Onset (ys) Fundoscopy Color Vision Perimetry ERG Cone (μV), † ERG Rod (μV), † OD OS OD OS OD OS 9250 M 30 1622T→C; 3113C→T 194G→A CF CF 6 Pigment clumping in the macula NP Large central scotoma over 40° ND, ‡ ND, ‡ 9303 M 21 1622T→C; 3113C→T 20/400 20/400 7 Granular pigmentary changes in the macula Diffusely disturbed Central scotoma of 20° Severely decreased, § Severely decreased, § 9369 F 40 6601-6602deIAG LP LP 8 Irregular hypopigmentation, mainly in the posterior pole. In later stages: attenuated vessels and bone spicula temporal to the macula Red-green defect Central scotoma varying from 10–30° 65 (65%) 80 (80%), ∥ 140 (90%) 160 (nl), ∥ 9370 M 15 1622T→C; 3113C→T 20/200 20/200 7 Granular aspect of the macula NP Concentric central scotoma of 8° 10 (13%) 9 (13%), ¶ 29 (29%) 29 (23%), ¶ 9371 M 38 1622T→C; 3113C→T 1622T→C;3113C→T 20/400 20/400 10 Bull’s eye maculopathy Red-green defect Concentric central scotoma of 20° NP 29 (16%), ‡ NP 54 (30%), ‡ 9378 F 50 768G→T CF CF 12 Bull’s eye maculopathy, narrow vessels in periphery with mild granular changes of the pigment epithelium and confluent patches of chorioretinal atrophy Severely disturbed Large, absolute, paracentral scotomas, relative scotoma centrally 20 (20%) 30 (30%), ∥ 70 (47%) 90 (60%), ∥ 9553 F 45 2588G→C IVS35del-2→+2del4 20/400 20/400 25 Bull’s eye maculopathy. Peripheral diffuse motting of RPE Severely disturbed Large central scotoma over 40° 14 (14%) 19 (19%), ¶ 41 (41%) 24 (24%), ¶ 9633 M 22 1622T→C; 3113C→T 4469G→A 20/400 20/200 12 Atrophy of retinal pigment epithelium in posterior pole. Early stages of bull’s eye maculopathy Red-green defect Central scotoma of 20° 12 (16%) 12 (16%), ¶ 61 (62%) 39 (39%), ¶ 9650 F 20 3364G→A 20/400 20/400 5 Central granular aspect Red-green defect Large central scotoma of 30° and relative constriction of III-4 70 (39%) 106 (59%), ‡ 272 (nl) 115 (76%), ‡ 10125 M 30 IVS30+1G→T 3085C→T 20/200 20/200 8 Central hypopigmentation with dark surrounding, resembling bull’s eye. Later in life: peripheral changes characteristic of RP Severe red-green defect; mild blue-yellow defect Central scotoma of 10–15° with mild peripheral restriction 75 (75%) 80 (80%), ∥ 130 (87%) 140 (93%), ∥ 11872 M 30 634C→T 20/200 20/200 10 Bull’s eye pattern Severely disturbed; blue-yellow more than red-green Central scotoma of 25° 23 (23%) 35 (35%), ∥ 110 (73%) 95 (63%), ∥ 13163 M 15 1622T→C;3113C→T IVS36+1G→A 20/400 20/200 6 Granular aspect of retinal pigment epithelium in macula. Slightly pale optic disc Severely disturbed Central scotoma of 10–15,° no peripheral involvement ND, ¶ ND, ¶  CF, count fingers; LP, light perception; ND, not detectable; NP, not performed. *  Allele 1, first line; allele 2, second line. †  Between parentheses: percentage of the ERG value compared to the lower limit of the normality; normal ERG values are indicated nl. ‡  Minimal values for ERG recordings: 150 μV for the photopic ERG, 180 μV for the scotopic ERG. §  ERG performed with skin electrodes. ∥  Minimal values for ERG recordings: 100 μV for the photopic ERG, 150 μV for the scotopic ERG. ¶  Minimal values for ERG recordings: 99 μV for the photopic ERG, 75 μV for the scotopic ERG. Figure 1. View OriginalDownload Slide (A–D) Fundus photographs and fluorescein angiograms in eyes of patients with (atypical) CRD. (A) Patient 11872 with bull’s eye maculopathy. (B) Patient 9369, demonstrating CRD in the later stages with attenuation of the retinal arterioles and irregular pigmentation temporal to the macula. (C) Fluorescein angiograms in patient 9378 showing confluent patches of chorioretinal atrophy. (D) Patient 10125 with central hypofluorescence enclosed by an ellipsoid hyperfluorescent area. In the surrounding area, hyperfluorescent flecks are visible, and the choroidal background fluorescence seems blocked, as seen in STGD.

Supplementary Materials

ABCA4ARc.[1957C > T];[4605insT]WESHuang et al., 2013cHuang et al., 2013c, Rivera et al., 2000

ABCA4

Supplement 3iovs-63-2-11_s003.pdf (1.1M)GUID: 00045B54-7E12-4EE1-B50D-27CAC38DD633

We identified 255 patients (87.9 %) harboring biallelic ABCA4 variants, 27 probands (9.3 %) with two or three variants but lacking familial segregation analysis, and eight patients (2.8 %) with monoallelic ABCA4 variants (Supplemental Table S4). We detected 268 distinct ABCA4 variants, consisting of 114 missense, 35 nonsense, 34 frameshift deletion or insertion, 31 canonical splice variants, 13 noncanonical splice site variants, 9 in-frame deletion or insertion, 9 DIVs, 4 structural variations, and 19 complex variants (Fig. 2).

MD-0084 STGD1 47 c.6410G>A p.(Cys2137Tyr) 47 c.6410G>A p.(Cys2137Tyr) Yes 7 7 - 23y - <0.05/<0.05 Riveiro-Alvarez et al.,2013

MD-0247ABCA423c.3386G>Tp.Arg1129Leu47c.6410G>Ap.Cys2137Tyr12YesABCR400 + dHPLC + HRMAguirre-Lamban et al. 2009 (8); Aguirre-Lamban et al. 2010 (16)

In 20 patients (19 STGD and 1 CRD), 18 different genotypes were identified (Table 1). Except p.Arg187His and p.Tyr954Ser variants, the rest of changes were previously reported as disease-associated allele. 14 The p.Arg187His and p.Tyr954Ser variants were not found in 100 ethnically matched control chromosomes. All the mutations identified in the 20 patients except one were detected by HRM for sensitivity of 95%; however, only 16 variants were identified by dHPLC for sensitivity of 80%.  Table 1. View Table Mutations AnalyzedTable 1. Mutations Analyzed Family Exon Genotype Mutation Detected by dHPLC Mutation Detected by HRM Nucleotide Change Amino Acid Change ARDM-167 5 c.560G>A p.Arg187His No Yes ARDM-257 5 c.560G>A p.Arg187His No Yes ARDM-164 6 c.700C>T p.Gln234X Yes Yes ARDM-135 8 c.1029_1030insT p.Asn344fsX Yes No ARDM-240 15 c.2285C>A p.Ala762Glu Yes Yes ARDM-248 19 c.2861A>C p.Tyr954Ser Yes Yes ARDM-90 — IVS21-2A>T — Yes Yes ARDM-40 27 c.3943C>T p.Gln1315X Yes Yes ARDM-158 30 c.4537delC p.Gln1513fsX1525 Yes Yes ARDM-38 33 c.4739delT p.Leu1580fs Yes Yes ARDM-163 36 c.5172G>T p.Trp1724Cys Not Yes ARDM-197 36 c.5172G>T p.Trp1724Cys Yes Yes ARDM-181 — IVS38+5G>A — Yes Yes ARDM-125 40 — p.KNLFA1876dup Yes Yes ARDM-183 43 c.5929G>A(False −) p.Gly1977Ser(False −) Yes Yes ARDM-146 44 c.6140T>A p.lle2047Asn Yes Yes ARDM-174 — IVS44+2T>A — Yes Yes ARDM-247 47 c.6410G>A p.Cys2137Tyr* Yes Yes ARDM-84 47 c.6410G>A p.Cys2137Tyr† No Yes ARDM-225 48 c.6559C>T p.Gln2187X Yes Yes  Previously unreported mutations are shown in bold. *  Mutation in heterozygous. †  Mutation in homozygous. Homozygous sequence alteration (p.Cys2137Tyr) could be identified from wild-type by HRM analyses (Fig. 1). In contrast, dHPLC did not distinguish any homozygous mutation, except when we mixed it, in a 1:1 proportion, with a previously sequenced wild-type sample at the end of each PCR session and before heteroduplex formation.

In Mexican patients, p.A1773V and p.G818E were identified in 17% and 15%, respectively, of the total mutant alleles.

Mutation scanning and direct DNA sequencing of all 50 exons of ABCR were completed for 150 families segregating recessive Stargardt disease (STGD1). ABCR variations were identified in 173 (57%) disease chromosomes, the majority of which represent missense amino acid substitutions. These ABCR variants were not found in 220 unaffected control individuals (440 chromosomes) but do cosegregate with the disease in these families with STGD1, and many occur in conserved functional domains. Missense amino acid substitutions located in the amino terminal one-third of the protein appear to be associated with earlier onset of the disease and may represent misfolding alleles. The two most common mutant alleles, G1961E and A1038V, each identified in 16 of 173 disease chromosomes, composed 18.5% of mutations identified. G1961E has been associated previously, at a statistically significant level in the heterozygous state, with age-related macular degeneration (AMD). Clinical evaluation of these 150 families with STGD1 revealed a high frequency of AMD in first- and second-degree relatives. These findings support the hypothesis that compound heterozygous ABCR mutations are responsible for STGD1 and that some heterozygous ABCR mutations may enhance susceptibility to AMD.

Mutation scanning and direct DNA sequencing of all 50 exons of ABCR were completed for 150 families segregating recessive Stargardt disease (STGD1). ABCR variations were identified in 173 (57%) disease chromosomes, the majority of which represent missense amino acid substitutions. These ABCR variants were not found in 220 unaffected control individuals (440 chromosomes) but do cosegregate with the disease in these families with STGD1, and many occur in conserved functional domains. Missense amino acid substitutions located in the amino terminal one-third of the protein appear to be associated with earlier onset of the disease and may represent misfolding alleles. The two most common mutant alleles, G1961E and A1038V, each identified in 16 of 173 disease chromosomes, composed 18.5% of mutations identified. G1961E has been associated previously, at a statistically significant level in the heterozygous state, with age-related macular degeneration (AMD). Clinical evaluation of these 150 families with STGD1 revealed a high frequency of AMD in first- and second-degree relatives. These findings support the hypothesis that compound heterozygous ABCR mutations are responsible for STGD1 and that some heterozygous ABCR mutations may enhance susceptibility to AMD.

Comparably, the result of the CNTNAP2 rs2710102 associations with ASD studies (n = 4+current study) was also not significant [n = 7276; p = 0.26; OR = 1.028 (95 % CI 0.98–1.08), see Suppl. Table S6, Fig. 1b]

he meta-analysis of the CNTNAP2 rs7794745 associations with ASD studies (n = 5+current study) did not result in significant association with ASD in general [n = 8576; p = 0.112; OR = 1.023 (95 % CI 0.99–1.05); see Suppl. Table S5, Fig. 1a]. Since we detected some heterogeneity for the SNP rs7794745 according to the funnel plot (see Suppl. Figure S10), we performed an additional meta-analysis synthesis using the random effect model. However, no significant association with ASD was observed and OR were very similar as for the fixed-model [OR = 1.081 (95 % CI 0.976–1.196), p = 0.133; for details Suppl. Table S9a].

single previously reported pathogenic variant c.4685 T > C, p.(I1562T) [1], in the proband (II/2, Fig. 3)