Genetic investigation of 93 families with microphthalmia or posterior microphthalmos.

Microphthalmia is a developmental eye defect that is highly variable in severity and in its potential for systemic association. Despite the discovery of many disease genes in microphthalmia, at least 50% of patients remain undiagnosed genetically. Here, we describe a cohort of 147 patients (93 families) from our highly consanguineous population with various forms of microphthalmia (including the distinct entity of posterior microphthalmos) that were investigated using a next-generation sequencing multi-gene panel (i-panel) as well as whole exome sequencing and molecular karyotyping. A potentially causal mutation was identified in the majority of the cohort with microphthalmia (61%) and posterior microphthalmos (82%). The identified mutations (55 point mutations, 15 of which are novel) spanned 24 known disease genes, some of which have not or only very rarely been linked to microphthalmia (PAX6, SLC18A2, DSC3 and CNKSR1). Our study has also identified interesting candidate variants in 2 genes that have not been linked to human diseases (MYO10 and ZNF219), which we present here as novel candidates for microphthalmia. In addition to revealing novel phenotypic aspects of microphthalmia, this study expands its allelic and locus heterogeneity and highlights the need for expanded testing of patients with this condition.

A common variant association study in ethnic Saudi Arabs reveals novel susceptibility loci for hypertriglyceridemia.

Hypertriglyceridemia (hTG) is a lipid disorder, resulting from an elevation in triglyceride levels, with a strong genetic component. It constitutes a significant risk factor for coronary artery disease (CAD), a leading cause of death worldwide. In this study, we performed a common variant association study for hTG in ethnic Saudi Arabs. We genotyped 5501 individuals in a two-phase experiment using Affymetrix Axiom® Genome-Wide CEU 1 Array (Affymetrix, Santa Cruz, CA) that contains a total of 587,352 single nucleotide polymorphisms (SNPs). The lead variant was the rs1558861 [1.99 (1.73-2.30); p = 7.37 × 10-22 ], residing on chromosome (chr) 11 at the apolipoprotein A-I/A-5 (APOA1/APOA5) locus. The rs780094 [1.34 (1.21-1.49); p = 8.57 × 10-8 ] on chr 2 at the glucokinase regulatory protein (GCKR) locus was similarly significantly associated, while the rs10911205 [1.29 (1.16-1.44); p = 3.52 × 10-6 ] on chr1 at the laminin subunit gamma-1 (LAMC1) locus showed suggestive association with disease. Furthermore, the rs17145738 [0.68 (0.60-0.77); p = 6.69 × 10-9 ] on chr7 at the carbohydrate-responsive element-binding protein-encoding (MLXIPL) gene locus displayed significant protective characteristics, while another variant rs6982502 [0.76 (0.68-0.84); p = 5.31 × 10-7 ] on chr8 showed similar but weaker properties. These findings were replicated in 317 cases vs 1415 controls from the same ethnic Arab population. Our study identified several variants across the human genome that are associated with hTG in ethnic Arabs.

Clinical genomics expands the morbid genome of intellectual disability and offers a high diagnostic yield.

Intellectual disability (ID) is a measurable phenotypic consequence of genetic and environmental factors. In this study, we prospectively assessed the diagnostic yield of genomic tools (molecular karyotyping, multi-gene panel and exome sequencing) in a cohort of 337 ID subjects as a first-tier test and compared it with a standard clinical evaluation performed in parallel. Standard clinical evaluation suggested a diagnosis in 16% of cases (54/337) but only 70% of these (38/54) were subsequently confirmed. On the other hand, the genomic approach revealed a likely diagnosis in 58% (n=196). These included copy number variants in 14% (n=54, 15% are novel), and point mutations revealed by multi-gene panel and exome sequencing in the remaining 43% (1% were found to have Fragile-X). The identified point mutations were mostly recessive (n=117, 81%), consistent with the high consanguinity of the study cohort, but also X-linked (n=8, 6%) and de novo dominant (n=19, 13%). When applied directly on all cases with negative molecular karyotyping, the diagnostic yield of exome sequencing was 60% (77/129). Exome sequencing also identified likely pathogenic variants in three novel candidate genes (DENND5A, NEMF and DNHD1) each of which harbored independent homozygous mutations in patients with overlapping phenotypes. In addition, exome sequencing revealed de novo and recessive variants in 32 genes (MAMDC2, TUBAL3, CPNE6, KLHL24, USP2, PIP5K1A, UBE4A, TP53TG5, ATOH1, C16ORF90, SLC39A14, TRERF1, RGL1, CDH11, SYDE2, HIRA, FEZF2, PROCA1, PIANP, PLK2, QRFPR, AP3B2, NUDT2, UFC1, BTN3A2, TADA1, ARFGEF3, FAM160B1, ZMYM5, SLC45A1, ARHGAP33 and CAPS2), which we highlight as potential candidates on the basis of several lines of evidence, and one of these genes (SLC39A14) was biallelically inactivated in a potentially treatable form of hypermanganesemia and neurodegeneration. Finally, likely causal variants in previously published candidate genes were identified (ASTN1, HELZ, THOC6, WDR45B, ADRA2B and CLIP1), thus supporting their involvement in ID pathogenesis. Our results expand the morbid genome of ID and support the adoption of genomics as a first-tier test for individuals with ID.

A common variant association study reveals novel susceptibility loci for low HDL-cholesterol levels in ethnic Arabs.

The genetic susceptibility to acquiring low high density lipoprotein-cholesterol (LHDLC) levels is not completely elucidated yet. In this study, we performed a common variant association study for harboring this trait in ethnic Arabs. We employed the Affymetrix high-density Axiom Genome-Wide ASI Array (Asian population) providing a coverage of 598,000 single nucleotide variations (SNPs) to genotype 5495 individuals in a two-phase study involving discovery and validation sets of experiments. The rs1800775 [1.31 (1.22-1.42); p = 3.41E-12] in the CETP gene and rs359027 [1.26 (1.16-1.36); p = 2.55E-08] in the LMCD1 gene were significantly associated with LHDLC levels. Furthermore, rs3104435 [1.26 (1.15-1.38); p = 1.19E-06] at the MATN1 locus, rs9835344 [1.16 (1.08-1.26); p = 8.75E-06] in the CNTN6 gene, rs1559997 [1.3 (1.14-1.47); p = 9.48E-06] in the SDS gene and rs1670273 [1.2 (1.1-1.31); p = 4.81E-06] in the DMN/SYNM gene exhibited suggestive association with the disorder. Seven other variants including rs1147169 in the PLCL1 gene, rs10248618 in the DNAH11, rs476155 in the GLIS3, rs7024300 in the ABCA1, intergenic rs10836699, rs11603691 in P2RX3 and rs750134 in CORO1C gene exhibited borderline protective properties. Validation and joint meta-analysis resulted in rs1800775, rs3104435 and rs359027 retaining their predisposing properties, while rs10836699 and rs11603691 showed protective properties. Our data show several predisposing variants across the genome for LHDLC levels in ethnic Arabs.

Mutation of the slow myosin heavy chain rod domain underlies hyaline body myopathy.

OBJECTIVE: To identify the gene and specific mutation underlying hyaline body myopathy in the family studied. METHODS: A microsatellite-based whole genome scan was performed. Linkage analysis assumed autosomal dominant inheritance and equal allele frequencies. A candidate gene approach within the linked interval and direct sequencing were used for mutation detection. RESULTS: Initial analysis indicated a maximum lod score of 3.01 at D14S1280. High-density mapping surrounding the linked locus was performed. Multipoint analysis showed that the linked region with a maximum lod score of 3.01 extended from D14S742 to D14S608 with a peak non-parametric linkage (NPL) score of 3.75 at D14S608. The myosin heavy chain genes MYH6 and MYH7 map to the region between D14S742 and D14S1280. Sequence analysis of the coding regions of MYH7 revealed an A-->T transversion at nucleotide position 25596 (M57965) resulting in a histidine-to-leucine amino acid change at residue 1904 (H1904L). CONCLUSION: Pathogenicity of the MYH7 H1904L mutation most likely results from disruption of myosin heavy chain assembly or stability of the sarcomeric protein. The MYH7 tail domain mutation results in an inclusion body myopathy with an apparent absence of hypertrophic cardiomyopathy usually associated with mutations of this gene.

Beneficial effects of lamivudine in hepatitis B virus-related decompensated cirrhosis.

BACKGROUND/AIMS: HBV-related chronic liver disease patients often present with hepatic decompensation and are not eligible for interferon therapy. Whether long-term lamivudine is effective in these patients was prospectively evaluated. METHODS: Eighteen patients with HBV-related decompensated cirrhosis, all with quantitative DNA +ve and 10 HBeAg +ve, were given lamivudine 150 mg/d. RESULTS: Each patient received at least 9 months (mean 17.9) of lamivudine. Three HBeAg+ve patients (30%) seroconverted to anti-HBe and one lost HBsAg during the follow-up. An improvement from baseline in the aspartate aminotransferase (130 vs. 72 IU/l, p<0.04); alanine aminotransferase (111 vs. 58 IU/l, p<0.01) and Child-Pugh score (8.3 vs 6.7, p<0.013) was seen. Lamivudine had no significant side-effects. HBV DNA became undetectable in all patients by 8 weeks of therapy. In three (17%) patients, HBV DNA again became positive at 9, 9 and 27 months. YMDD mutant was, however, detected in only one (6%). A significant reduction was noted in the morbidity and hospitalizations for complications of liver disease before and after starting lamivudine (1.5+/-0.7 vs. 0.6+/-0.7, p<0.002). CONCLUSIONS: In decompensated HBV-related cirrhosis, lamivudine: i) is effective in suppressing HBV DNA and seroconversion to anti-HBe (30%), ii) can achieve significant improvement in clinical and biochemical status of liver functions.