Genotype-phenotype analysis of Jervell and Lange-Nielsen syndrome in six families from Saudi Arabia.

We sought to explore the genotype-phenotype of Jervell and Lange-Nielsen syndrome (JLNS) patients in Saudi Arabia. We have also assessed the plausible effect of consanguinity into the pathology of JLNS. Six families with at least one JLNS-affected member attended our clinic between 2011 and 2013. Retrospective and prospective clinical data were collected and genetic investigation was performed. Pathogenic mutations in the KCNQ1 gene were detected in all JLNS patients. The homozygous mutations detected were Leu273Phe, Asp202Asn, Ile567Thr, and c.1486_1487delCT and compound heterozygous mutations were c.820_ 830del and c.1251+1G>T. All living JLNS patients except one had a QTc of >500 ms and a history of recurrent syncope. ß-Blockers abolished the cardiac-related events in all patients except two siblings with homozygous Ile567Thr mutation. Four of the six mutations were originally reported in autosomal dominant long QT syndrome (LQTS) patients. Eighty percent of the heterozygote mutation carriers showed prolongation of QTc, but majority of these reported no symptoms attributable to arrhythmias. Mutations detected in this study will be advantageous in tribe and region-specific cascade screening of LQTS in Saudi Arabia.

Prevalence and characteristics of non-syndromic orofacial clefts and the influence of consanguinity.

UNLABELLED: The Objective of this study was to identify the prevalence and describe the characteristics of non-syndromic orofacial cleft (NSOFC) in Jeddah, Saudi Arabia and examine the influence of consanguinity. STUDY DESIGN: Six hospitals were selected to represent Jeddah's five municipal districts. New born infants with NSOFC born between 1st of January 2010 to 31st of December 2011 were clinically examined and their number compared to the total number of infants born in these hospitals to calculate the prevalence of NSOFC types and sub-phenotypes. Referred Infants were included for the purpose of studying NSOFC characteristics and their relationship to consanguinity. Information on NSOFC infants was gathered through parents' interviews, infants 'files and patient examinations. RESULTS: Prospective surveillance of births resulted in identifying 37 NSOFC infants born between 1st of January 2010 to 31st of December 2011 giving a birth prevalence of 0.80/1000 living births. The total infants seen, including referred cases, were 79 children. Consanguinity among parents of cleft palate (CP) cases was statistically higher than that among cleft lip with or without cleft palate (CL/P) patients (P = 0.039). Although there appears to be a trend in the relationship between consanguinity and severity of CL/P sub-phenotype, it was not statistically significant (P = 0.248). CONCLUSIONS: Birth prevalence of NSOFC in Jeddah City was 0.8/1000 live births with CL/P: 0.68/1000 and CP: 0.13/1000. Both figures were low compared to the global birth prevalence (NSOFC: 1.25/1000, CL/P: 0.94/1000 and CP: 0.31/1000 live births). Consanguineous parents were statistically higher among CP cases than among other NSOFC phenotypes.

De novo mutation in the KCNQ1 gene causal to Jervell and Lange-Nielsen syndrome.

Jervell and Lange-Nielsen syndrome (JLNS) is an autosomal recessive disorder, clinically characterized by severe cardiac arrhythmias [due to prolonged QTc interval in electrocardiogram (ECG)] and bilateral sensory neural deafness. Molecular defects causal to JLNS are either homozygous or compound heterozygous mutations, predominantly in the KCNQ1 gene and occasionally in the KCNE1 gene. As the molecular defect is bi-allelic, JLNS patients inherit one pathogenic mutation causal to the disorder from each parent. In this report, we show for the first time that such a disorder could also occur due to a spontaneous de novo mutation in the affected individual, not inherited from the parent, which makes this case unique unlike the previously reported JLNS cases.

A human iPSC model of Ligase IV deficiency reveals an important role for NHEJ-mediated-DSB repair in the survival and genomic stability of induced pluripotent stem cells and emerging haematopoietic progenitors.

DNA double strand breaks (DSBs) are the most common form of DNA damage and are repaired by non-homologous-end-joining (NHEJ) or homologous recombination (HR). Several protein components function in NHEJ, and of these, DNA Ligase IV is essential for performing the final 'end-joining' step. Mutations in DNA Ligase IV result in LIG4 syndrome, which is characterised by growth defects, microcephaly, reduced number of blood cells, increased predisposition to leukaemia and variable degrees of immunodeficiency. In this manuscript, we report the creation of a human induced pluripotent stem cell (iPSC) model of LIG4 deficiency, which accurately replicates the DSB repair phenotype of LIG4 patients. Our findings demonstrate that impairment of NHEJ-mediated-DSB repair in human iPSC results in accumulation of DSBs and enhanced apoptosis, thus providing new insights into likely mechanisms used by pluripotent stem cells to maintain their genomic integrity. Defects in NHEJ-mediated-DSB repair also led to a significant decrease in reprogramming efficiency of human cells and accumulation of chromosomal abnormalities, suggesting a key role for NHEJ in somatic cell reprogramming and providing insights for future cell based therapies for applications of LIG4-iPSCs. Although haematopoietic specification of LIG4-iPSC is not affected per se, the emerging haematopoietic progenitors show a high accumulation of DSBs and enhanced apoptosis, resulting in reduced numbers of mature haematopoietic cells. Together our findings provide new insights into the role of NHEJ-mediated-DSB repair in the survival and differentiation of progenitor cells, which likely underlies the developmental abnormalities observed in many DNA damage disorders. In addition, our findings are important for understanding how genomic instability arises in pluripotent stem cells and for defining appropriate culture conditions that restrict DNA damage and result in ex vivo expansion of stem cells with intact genomes.

Smith-Lemli-Opitz syndrome among Arabs.

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder of variable presentation caused by the deficiency of the 3ß- hydroxycholesterol Δ(7) - reductase. Over the past 10 years, our biochemical laboratory has screened 191 plasma samples for possible SLOS, measuring the plasma cholesterol and 7-dehydrocholesterol using gas chromatography-mass spectrometry (GC-MS). The SLOS was confirmed in only five Arab patients with growth retardation, global developmental delay, dysmorphic features, and 2-3 toe syndactyly, among other findings. All cases represented moderate to severe form of SLOS. One patient had a unique cardiovascular malformation (cor triatriatum with significant obstruction of the right pulmonary veins). Two previously reported N287K (861 C>A) and R352Q (1055 G>A) and a novel R352L (1055 G>T) mutations were identified in the DHCR7 gene in these patients. The paper sheds light on this rare disease among Arabs and reviews all reported SLOS cases in the Arab population.