Libe Gradstein

High Myopia Caused by a Mutation in LEPREL1, Encoding Prolyl 3-Hydroxylase 2

Autosomal-recessive high-grade axial myopia was diagnosed in Bedouin Israeli consanguineous kindred. Some affected individuals also had variable expressivity of early-onset cataracts, peripheral vitreo-retinal degeneration, and secondary sight loss due to severe retinal detachments. Through genome-wide linkage analysis, the disease-associated gene was mapped to ∼1.7 Mb on chromosome 3q28 (the maximum LOD score was 11.5 at θ = 0 for marker D3S1314). Sequencing of the entire coding regions and intron-exon boundaries of the six genes within the defined locus identified a single mutation (c.1523G>T) in exon 10 of LEPREL1, encoding prolyl 3-hydroxylase 2 (P3H2), a 2-oxoglutarate-dependent dioxygenase that hydroxylates collagens. The mutation affects a glycine that is conserved within P3H isozymes. Analysis of wild-type and p.Gly508Val (c.1523G>T) mutant recombinant P3H2 polypeptides expressed in insect cells showed that the mutation led to complete inactivation of P3H2.

COL11A2 mutation associated with autosomal recessive Weissenbacher–Zweymuller syndrome: Molecular and clinical overlap with otospondylomegaepiphyseal dysplasia (OSMED)†

Autosomal recessive Weissenbacher–Zweymuller syndrome (WZS) is a skeletal dysplasia characterized by rhizomelic dwarfism and severe hearing loss. Mutations in the COL11A2 gene have been implicated in causing the autosomal dominant form of this syndrome as well as non‐ocular Stickler syndrome and the autosomal recessive syndrome otospondylomegaepiphyseal dysplasia (OSMED). In a consanguineous Bedouin tribe living in Southern Israel, five individuals affected by autosomal recessive WZS were available for genetic analysis. Homozygosity of a mutation in the COL11A2 gene was found in all affected individuals. This finding lends molecular support to the clinical notion that autosomal recessive WZS and OSMED are a single entity.

UNC80 mutation causes a syndrome of hypotonia, severe intellectual disability, dyskinesia and dysmorphism, similar to that caused by mutations in its interacting cation channel NALCN

Background A syndrome of profound hypotonia, intellectual disability, intrauterine growth retardation with subsequent failure to thrive, dyskinesia and epilepsy was diagnosed in Bedouin Israeli families. Mild dysmorphism was evident: plagiocephaly, broad forehead with prominent nose, smooth philtrum and congenital esotropia. We set out to decipher the molecular basis of this syndrome. Methods Genome-wide linkage analysis and fine mapping were done. Whole exome sequencing data were filtered for candidate variants within locus. Validation and segregation of the mutation was assayed via Sanger sequencing. UNC80 expression pattern was analysed through reverse transcription PCR. Results Homozygosity mapping followed by fine mapping identified a 7.5 Mb disease-associated locus (logarithm of odds score 3.5) on chromosome 2. Whole exome and Sanger sequencing identified a single homozygous nonsense mutation within this locus, segregating within the families as expected for recessive heredity and not found in a homozygous state in 150 Bedouin controls: c.151C>T, p.(R51*) in UNC80. Conclusions The syndrome described is caused by a mutation in UNC80, truncating most of the 3258 amino acids highly conserved encoded protein, that has no known motifs. UNC80 bridges between UNC79 and the cation channel NALCN, enabling NALCNs role in basal Na+ leak conductance in neurons, essential for neuronal function. The phenotype caused by the UNC80 mutation resembles that previously described for homozygous NALCN mutations.

Isolated foveal hypoplasia with secondary nystagmus and low vision is associated with a homozygous SLC38A8 mutation

Foveal hypoplasia, always accompanied by nystagmus, is found as part of the clinical spectrum of various eye disorders such as aniridia, albinism and achromatopsia. However, the molecular basis of isolated autosomal recessive foveal hypoplasia is yet unknown. Individuals of apparently unrelated non consanguineous Israeli families of Jewish Indian (Mumbai) ancestry presented with isolated foveal hypoplasia associated with congenital nystagmus and reduced visual acuity. Genome-wide homozygosity mapping followed by fine mapping defined a 830 Kb disease-associated locus (LOD score 3.5). Whole-exome sequencing identified a single missense mutation in the homozygosity region: c.95T>G, p.(Ile32Ser), in a conserved amino acid within the first predicted transmembrane domain of SLC38A8. The mutation fully segregated with the disease-associated phenotype, demonstrating an ∼10% carrier rate in Mumbai Jews. SLC38A8 encodes a putative sodium-dependent amino-acid/proton antiporter, which we showed to be expressed solely in the eye. Thus, a homozygous SLC38A8 mutation likely underlies isolated foveal hypoplasia.

SLC30A9 mutation affecting intracellular zinc homeostasis causes a novel cerebro-renal syndrome

Few cerebro-renal syndromes have been described to date. Perez et al. identify a novel autosomal recessive cerebro-renal syndrome in a consanguineous Bedouin kindred, caused by a mutation in SLC30A9. The mutation disrupts the role of SLC30A9 in Zn2+ transport, leading to impaired regulation of cytosolic zinc homeostasis.

The ocular manifestations of Weissenbacher-Zweymuller syndrome.

AbstractPurpose Weissenbacher–Zweymuller syndrome (WZS) is an autosomal recessive disorder of delayed skeletal maturation. Its characteristic features include rhizomelic dwarfism with metaphyseal and vertebral changes. It has been challenged whether WZS is a part of the spectrum of Stickler syndrome. We report ocular findings in the largest ever-presented series of patients with WZS.Methods Patients underwent a paediatric examination, including assessment of growth and development, genetic work-up and X-ray of vertebra and long bones. All had a complete ophthalmic examination, cycloplegic refraction, and face and body photography.Results All patients had hypertelorism and protruding eyes. Four patients had refractive errors necessitating optical correction ranging from +3 to –8 D. Two patients had strabismus. None had vitreoretinal degeneration, glaucoma, or cataract.Conclusions Ocular manifestations of WZS differ from those in Stickler syndrome, indicating that the two likely represent distinct clinical entities. Strabismus and various refractive errors often accompany WZS. An ophthalmologist should follow children with this disorder from an early age to prevent amblyopia.

A syndrome of congenital microcephaly, intellectual disability and dysmorphism with a homozygous mutation in FRMD4A

A consanguineous Bedouin Israeli kindred presented with a novel autosomal recessive intellectual disability syndrome of congenital microcephaly, low anterior hairline, bitemporal narrowing, low-set protruding ears, strabismus and tented thick eyebrows with sparse hair in their medial segment. Brain imaging demonstrated various degrees of agenesis of corpus callosum and hypoplasia of the vermis and cerebellum. Genome-wide linkage analysis followed by fine mapping defined a 7.67 Mb disease-associated locus (LOD score 4.99 at θ=0 for marker D10S1653). Sequencing of the 48 genes within the locus identified a single non-synonymous homozygous duplication frameshift mutation of 13 nucleotides (c.2134_2146dup13) within the coding region of FRMD4A, that was common to all affected individuals and not found in 180 non-related Bedouin controls. Three of 50 remotely related healthy controls of the same tribe were heterozygous for the mutation. FRMD4A, member of the FERM superfamily, is involved in cell structure, transport and signaling. It regulates cell polarity by playing an important role in the activation of ARF6, mediating the interaction between Par3 and the ARF6 guanine nucleotide exchange factor. ARF6 is known to modulate cell polarity in neurons, and regulates dendritic branching in hippocampal neurons and neurite outgrowth. The FRMD4 domain that is essential for determining cell polarity through interaction with Par3 is truncated by the c.2134_2146dup13 mutation. FRMD4A polymorphisms were recently suggested to be a risk factor for Alzheimer’s disease. We now show a homozygous frameshift mutation of the same gene in a severe neurologic syndrome with unique dysmorphism.

Genetic Analysis of the Rhodopsin Gene Identifies a Mosaic Dominant Retinitis Pigmentosa Mutation in a Healthy Individual.

Purpose Retinitis pigmentosa (RP) is a group of clinically and genetically heterogeneous hereditary retinal diseases that result in blindness due to photoreceptor degeneration. Mutations in the rhodopsin (RHO) gene are the most common cause of autosomal dominant RP (adRP) and are responsible for 16% to 35% of adRP cases in the Western population. Our purpose was to investigate the contribution of RHO to adRP in the Israeli and Palestinian populations. Methods Thirty-two adRP families participated in the study. Mutation detection was performed by whole exome sequencing (WES) and Sanger sequencing of RHO exons. Fluorescence PCR reactions of serially diluted samples were used to predict the percentage of mosaic cells in blood samples. Results Eight RHO disease-causing mutations were identified in nine families, with only one novel mutation, c.548-638dup91bp, identified in a family where WES failed to detect any causal variant. Segregation analysis revealed that the origin of the mutation is in a mosaic healthy individual carrying the mutation in approximately 13% of blood cells. Conclusions This is the first report of the mutation spectrum of a known adRP gene in the Israeli and Palestinian populations, leading to the identification of seven previously reported mutations and one novel mutation. Our study shows that RHO mutations are a major cause of adRP in this cohort and are responsible for 28% of adRP families. The novel mutation exhibits a unique phenomenon in which an unaffected individual is mosaic for an adRP-causing mutation.

CDC174, a novel component of the exon junction complex whose mutation underlies a syndrome of hypotonia and psychomotor developmental delay

Siblings of non-consanguineous Jewish-Ethiopian ancestry presented with congenital axial hypotonia, weakness of the abducens nerve, psychomotor developmental delay with brain ventriculomegaly, variable thinning of corpus callosum and cardiac septal defects. Homozygosity mapping identified a single disease-associated locus of 3.5 Mb on chromosome 3. Studies of a Bedouin consanguineous kindred affected with a similar recessive phenotype identified a single disease-associated 18 Mb homozygosity locus encompassing the entire 3.5 Mb locus. Whole exome sequencing demonstrated only two homozygous mutations within a shared identical haplotype of 0.6 Mb, common to both Bedouin and Ethiopian affected individuals, suggesting an ancient common founder. Only one of the mutations segregated as expected in both kindreds and was not found in Bedouin and Jewish-Ethiopian controls: c.1404A>G, p.[*468Trpext*6] in CCDC174. We showed that CCDC174 is ubiquitous, restricted to the cell nucleus and co-localized with EIF4A3. In fact, yeast-two-hybrid assay demonstrated interaction of CCDC174 with EIF4A3, a component of exon junction complex. Knockdown of the CCDC174 ortholog in Xenopus laevis embryos resulted in poor neural fold closure at the neurula stage with later embryonic lethality. Knockdown embryos exhibited a sharp reduction in expression of n-tubulin, a marker for differentiating primary neurons, and of hindbrain markers krox20 and hoxb3. The Xenopus phenotype could be rescued by the human normal, yet not the mutant CCDC174 transcripts. Moreover, overexpression of mutant but not normal CCDC174 in neuroblastoma cells caused rapid apoptosis. In line with the hypotonia phenotype, the CCDC174 mutation caused depletion of RYR1 and marked myopathic changes in skeletal muscle of affected individuals.

Carrier frequency analysis of mutations causing autosomal-recessive-inherited retinal diseases in the Israeli population

Inherited retinal diseases (IRDs) are heterogeneous phenotypes caused by variants in a large number of genes. Disease prevalence and the frequency of carriers in the general population have been estimated in only a few studies, but are largely unknown. To this end, we developed two parallel methods to calculate carrier frequency for mutations causing autosomal-recessive (AR) IRDs in the Israeli population. We created an SQL database containing information on 178 genes from gnomAD (including genotyping of 5706 Ashkenazi Jewish (AJ) individuals) and our cohort of >2000 families with IRDs. Carrier frequency for IRD variants and genes was calculated based on allele frequency values and the Hardy–Weinberg (HW) equation. We identified 399 IRD-causing variants in 111 genes in Israeli patients and AJ controls. For the AJ subpopulation, gnomAD and HW-based regression analysis showed high correlation, therefore allowing one to use HW-based data as a reliable estimate of carrier frequency. Overall, carrier frequency per subpopulation ranges from 1/2.2 to 1/9.6 individuals, with the highest value obtained for the Arab-Muslim subpopulation in Jerusalem reaching an extremely high carrier rate of 44.7%. Carrier frequency per gene ranges from 1/31 to 1/11994 individuals. We estimate the total carrier frequency for AR-IRD mutations in the Israeli population as over 30%, a relatively high carrier frequency with marked variability among subpopulations. Therefore, these data are highly important for more reliable genetic counseling and genetic screening. Our method can be adapted to study other populations, either based on allele frequency data or cohort of patients.