Founder mutation for Huntington disease in Caucasus Jews.

Huntington disease (HD), an autosomal dominant disorder involving HTT, is characterized by chorea, psychiatric illness and cognitive decline. Diagnosis and age of onset depend on the degree of expansion of the trinucleotide CAG repeat within the gene. The prevalence of HD is known for Europeans but has not been studied in the Israeli population. Between 2006 and 2011 we diagnosed in our adult genetics clinic ten HD probands, nine of whom were Caucasus Jews (CJ) (Azerbaijani), and one Ashkenazi Jewish. We performed haplotype analysis to look for evidence of a founder mutation, and found that of the nine CJ, eight shared the same haplotype that was compatible with the A1 haplogroup. We calculated the coalescence age of the mutation to be between 80 and 150 years. Ninety percent of our HD patients are CJ, as are 27% of the HD patients in Israel, although the CJ comprise only 1.4% of the Israeli population. Our findings suggest a higher prevalence of HD among CJ compared to the general Israeli population and are consistent with a recent founder mutation. We recommend a higher degree of suspicion for HD in CJ with subtle clinical findings.

Early metabolic defects in Arab subjects with strong family history of Type 2 diabetes.

AIMS AND OBJECTIVE: It is widely accepted that the genetic make-up of the subject plays a pivotal role in the development of insulin resistance and ß cell failure. The objective of this study was to examine whether the same or distinct genetic backgrounds contribute to the development of insulin resistance and ß cell failure. METHODS: We examined insulin sensitivity and ß cell function in lean normal glucose tolerance subjects from 3 multigeneration Arab families. Families 1 and 2 had strong history of Type 2 diabetes (T2DM), while no member of family 3 had T2DM. RESULTS: Subjects in family 1 manifested increased basal plasma free fatty acid (FFA) concentration and impaired suppression of plasma FFA during the OGTT compared to subjects in family 3. Subjects in family 2 had comparable fasting plasma FFA and suppression of plasma FFA during the OGTT to family 3. Both the absolute plasma glucose concentrations, and incremental area under the plasma glucose curve (ΔG0-120) during the OGTT were comparable in subjects of families 1 and 2, and were decreased in subjects of family 3. Whole body and muscle insulin sensitivity were comparable in subjects from families 2 and 3, and both were significantly decreased in subjects of family 1. Beta cell function was comparable in subjects of families 1 and 3 and was significantly decreased in subjects of family 2. CONCLUSION: These results demonstrate that distinct genetic background contributes to the development of insulin resistance and ß cell dysfunction in Arab individuals.

Heterozygous mutations in ANKH, the human ortholog of the mouse progressive ankylosis gene, result in craniometaphyseal dysplasia.

Craniometaphyseal dysplasia (CMD) is a bone dysplasia characterized by overgrowth and sclerosis of the craniofacial bones and abnormal modeling of the metaphyses of the tubular bones. Hyperostosis and sclerosis of the skull may lead to cranial nerve compressions resulting in hearing loss and facial palsy. An autosomal dominant form of the disorder (MIM 123000) was linked to chromosome 5p15.2-p14.1 (ref. 3) within a region harboring the human homolog (ANKH) of the mouse progressive ankylosis (ank) gene. The ANK protein spans the outer cell membrane and shuttles inorganic pyrophosphate (PPi), a major inhibitor of physiologic and pathologic calcification, bone mineralization and bone resorption. Here we carry out mutation analysis of ANKH, revealing six different mutations in eight of nine families. The mutations predict single amino acid substitutions, deletions or insertions. Using a helix prediction program, we propose for the ANK molecule 12 membrane-spanning helices with an alternate inside/out orientation and a central channel permitting the passage of PPi. The mutations occur at highly conserved amino acid residues presumed to be located in the cytosolic portion of the protein. Our results link the PPi channel ANK with bone formation and remodeling.

Identification of 11 novel mutations in eight BBS genes by high-resolution homozygosity mapping.

BACKGROUND: Bardet-Biedl syndrome (BBS) is primarily an autosomal recessive disorder characterised by the five cardinal features retinitis pigmentosa, postaxial polydactyly, mental retardation, obesity and hypogenitalism. In addition, renal cysts and other anomalies of the kidney and urinary tract can be present. To date, mutations in 12 BBS genes as well as in MKS1 and CEP290 have been identified as causing BBS. The vast genetic heterogeneity of BBS renders molecular genetic diagnosis difficult in terms of the time and cost required to screen all 204 coding exons. METHOD: Here, the use of genome-wide homozygosity mapping as a tool to identify homozygous segments at known BBS loci, in BBS individuals from inbred and outbred background, is reported. RESULTS: In a worldwide cohort of 45 families, causative homozygous mutations in 20 families were identified via direct exon sequencing. Eleven of these mutations were novel, thereby increasing the number of known BBS mutations by 5% (11/218). CONCLUSIONS: Thus, in the presence of extreme genetic locus heterogeneity, homozygosity mapping provides a valuable approach to the molecular genetic diagnosis of BBS and will facilitate the discovery of novel pathogenic mutations.

Dependence of maternal serum [AFP]/[hCG] median ratios on age of gestation: comparison of trisomy 21 to euploid pregnancies.

BACKGROUND: Current risk calculations for trisomy 21, which are based on multiples of median (MoM), do not take into account possible differences between euploid and trisomy 21 pregnancies that may develop with gestational age. In order to optimize the predictive value of screening tests, we calculated the ratio between maternal serum concentration of alpha-fetoprotein (AFP) and that of human chorionic gonadotropin (hCG) in euploid and in trisomy 21 pregnancies. METHODS: The medians of the concentration ratios, [AFP]/[hCG] at 16-21 weeks of gestation, were plotted as a function of gestational age for 307 cases of trisomy 21 and were compared with the medians of 30 549 normal karyotype cases. RESULTS: [AFP]/[hCG] ratio medians were independent of body weight and maternal age. There was a significant difference in the [AFP]/[hCG] ratio when comparing trisomy 21 and euploid pregnancies at each week. This difference became greater with advancing gestational age (P < 0.01). CONCLUSION: There is a significant difference in ratios of [AFP]/[hCG] between euploid and trisomy 21 pregnancies, which may be used to improve detection rates of Down syndrome screening.

Osteosclerosis, hypoplastic nose, and proptosis (Raine syndrome): further delineation.

We describe a newborn girl with a lethal sclerosing bone dysplasia leading to prenatal skeletal alterations and microcephaly, proptosis, hypoplastic nose and midface, small jaw, cleft palate, hypertrophied gums, intracranial calcifications, and generalized osteosclerosis. There is a remarkable similarity between our patient and six previously reported infants subsequently categorized as having a distinct entity: Raine syndrome. Autosomal recessive inheritance is postulated based on parental consanguinity in several of the previous cases and in our patient.

Familial lethal skeletal dysplasia with cloverleaf skull and multiple anomalies of brain, eye, face and heart: a new autosomal recessive multiple congenital anomalies syndrome.

We report on a 'new' lethal familial short-limb bone dysplasia associated with multiple anomalies in three sibs born to Arabic-Muslim consanguineous healthy parents. Clinical abnormalities included short limbs and short hands, cloverleaf skull, frontal bossing, wide anterior fontanel, hypertelorism, bilateral microphthalmia, cataract, low-set ears, narrow chest, ambiguous genitalia, cardiac ventricular septal defect (VSD) and agenesis of the corpus callosum. Radiological abnormalities included cloverleaf skull, hypoplastic clavicles and scapulae, thin, wavy cupped ribs, flat vertebral bodies with coronal clefting and several unossified vertebral pedicles and hypo-ossification of the pubic bone. The main changes noted in the long bones consisted of short-bowed long bones with abnormal metaphyses and unossified epiphyses. Chondro-osseous morphology documented degenerating chondrocytes with disorganization of the hypertrophied cartilage and short disorganized columns of hypertrophied areas. An autosomal recessive mode of inheritance seems most likely.

Vitamin D resistant rickets with alopecia: a form of end organ resistance to 1,25 dihydroxy vitamin D.

A 4-year-old girl presented with severe clinical and radiological rickets, and alopecia since the age of 1 year. Laboratory studies revealed: hypocalcaemia, hypophosphataemia, secondary hyperparathyroidism, abnormally low intestinal calcium absorption, and markedly elevated circulating 1,25(OH)2D3 levels. A normal calcaemic response to parathyroid extract was obtained. Treatment attempts with vitamin D2, 1 alpha (OH)D3 and 1,25(OH)2D3 were totally ineffective. Intestinal resistance to the action of 1,25(OH)2D3 appeared well established in this case. Refractoriness of bone to this hormone seems less certain. From this new entity of 'Vitamin D resistant rickets due to end organ unresponsiveness', six cases have been hitherto reported in the literature. However, only two have enough resemblance to our case, to constitute a distinct and well defined nosologic subunit. The molecular basis of this disorder(s) remains to be elucidated.