Gain-of-function mutation of microRNA-140 in human skeletal dysplasia.

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression. Heterozygous loss-of-function point mutations of miRNA genes are associated with several human congenital disorders1-5, but neomorphic (gain-of-new-function) mutations in miRNAs due to nucleotide substitutions have not been reported. Here we describe a neomorphic seed region mutation in the chondrocyte-specific, super-enhancer-associated MIR140 gene encoding microRNA-140 (miR-140) in a novel autosomal dominant human skeletal dysplasia. Mice with the corresponding single nucleotide substitution show skeletal abnormalities similar to those of the patients but distinct from those of miR-140-null mice6. This mutant miRNA gene yields abundant mutant miR-140-5p expression without miRNA-processing defects. In chondrocytes, the mutation causes widespread derepression of wild-type miR-140-5p targets and repression of mutant miR-140-5p targets, indicating that the mutation produces both loss-of-function and gain-of-function effects. Furthermore, the mutant miR-140-5p seed competes with the conserved RNA-binding protein Ybx1 for overlapping binding sites. This finding may explain the potent target repression and robust in vivo effect by this mutant miRNA even in the absence of evolutionary selection of miRNA-target RNA interactions, which contributes to the strong regulatory effects of conserved miRNAs7,8. Our study presents the first case of a pathogenic gain-of-function miRNA mutation and provides molecular insight into neomorphic actions of emerging and/or mutant miRNAs.

Novel SMARCAL1 bi-allelic mutations associated with a chromosomal breakage phenotype in a severe SIOD patient.

PURPOSE: Chromosomal instability syndromes include a group of rare diseases characterized by defective DNA-damage-response and increased risk of chromosomal breakage. Patients display defects in the recognition and/or repair of DNA damage, with a subsequent high rate of malignancies and abnormal gene rearrangements. Other clinical manifestations, such as immunodeficiency, neurodevelopmental delay and skeletal abnormalities, are present in some of these syndromes. We studied a patient with profound T-lymphocyte defect, neurodevelopmental delay, facial dysmorphism, nephrotic syndrome and spondyloepiphyseal bone dysplasia typical of SIOD. METHODS: Karyotype and chromosome fragility assays on patients' peripheral blood mononuclear cells showed an abnormal rate of spontaneous breaks. Cell cycle analysis of patient's fibroblasts following replication stress induced by hydroxyhurea revealed a delay in their release from S-phase to G2. When using higher concentrations of hydroxyhurea no patient fibroblast colonies could survive, compared with control fibroblasts. Whole-exome sequencing revealed novel compound heterozygote mutations in SMARCAL1 gene, resulting in putative frame shifts of encoded SMARCAL1 from each allele and no detected protein in patient's cells. The patient's youngest brother was found to have similar manifestations of SIOD but of less severity, including short stature, facial dysmorphism and typical osseous dysplasia, but no clinical findings suggestive of immunodeficiency and no chromosomal fragility. Similar to his sister, the brother carries both bi-allelic mutations in SMARCAL1 gene. CONCLUSIONS: We present here the first evidence of intrinsic chromosomal instability in a severe SMARCAL1-deficient patient with a clinical picture of SIOD. Our results are consistent with the recently outlined role of SMARCAL1 protein in DNA damage response.

Dynamic modification strategy of the Israeli carrier screening protocol: inclusion of the Oriental Jewish Group to the cystic fibrosis panel.

PURPOSE: A retrospective population study was conducted to determine the carrier frequencies of recently identified mutations in Oriental Jewish cystic fibrosis patients. METHODS: Data were collected from 10 medical centers that screened the following mutations: two splice site mutations-3121-1G>A and 2751 + 1insT-and one nonsense mutation-the Y1092X in Iraqi Jews. One missense mutation, I1234V, was screened in Yemenite Jews. RESULTS: A total of 2499 Iraqi Jews were tested for one, two, or all three mutations. The 3121-1G>A, Y1092X, and 2751 + 1insT mutations had a carrier frequency of 1:68.5, 1:435, and 0, respectively. In 1435 Yemenite Jews screened, I1234V had a carrier frequency of 1:130. CONCLUSION: The 0.84% allele frequency of the three Iraqi founder mutations falls within the Israeli Society of Medical Geneticists' inclusion criteria for screening of 1:60 carrier frequency; hence, Iraqi Jews were added to the carrier screening policy with a panel including the three Iraqi founder mutations in addition to the five Ashkenazi mutations previously detected in Eastern Jews. 2751 + 1insT that was detected in patients only was included in the screening panel to increase the detection rate. I1234V does not meet the inclusion criteria but is now offered on a diagnostic basis and can be added to the screening panel for individuals whose mixed origin includes Yemenite, in addition to protocol-recommended origins. This study demonstrates the dynamic modifications of the Israeli carrier cystic fibrosis screening protocol based on newly detected founder mutations in a large cohort, taking into account mutation impact and intercommunal admixture.

Attitudes of Israeli Muslims at risk of genetic disorders towards pregnancy termination.

OBJECTIVES: (1) To examine attitudes towards termination of pregnancy (TOP) among high-risk and non-high-risk (for cystic fibrosis) Arab-Muslims, and (2) to examine the effect of an intervention, which among other things related explicitly to TOP. METHODS: The study comprised three groups: (1) an intervention group at high risk for CF, which received community genetic counseling; (2) a control group at high risk for CF, and (3) a control group from the general population. The latter two groups were exposed to minimal intervention. Attitudes were measured two or three times during a 1-year period (for the control and intervention groups, respectively). RESULTS: Predictors of an affected fetus being considered a legitimate cause for TOP were religiosity, familiarity with an affected child, and benefits of the test. Predictors of individuals (hypothetically) choosing abortion in the case of an affected fetus were education and age. No change occurred in the attitudes of participants (either experimental or control groups) in the course of 1 year. CONCLUSIONS: Other possible intervention options are discussed, and specifically, the advantages of using opinion leaders such as clergy and medical staff.