A founder mutation in the TCIRG1 gene causes osteopetrosis in the Ashkenazi Jewish population.

Osteopetrosis is a rare and heterogeneous genetic disorder characterized by dense bone mass that is a consequence of defective osteoclast function and/or development. Autosomal recessive osteopetrosis (ARO) is the most severe form and is often fatal within the first years of life; early hematopoietic stem cell transplant (HSCT) remains the only curative treatment for ARO. The majority of the ARO-causing mutations are located in the TCIRG1 gene. We report here the identification and characterization of an A to T transversion in the fourth base of the intron 2 donor splice site (c.117+4A→T) in TCIRG1, a mutation not previously seen in the Ashkenazi Jewish (AJ) population. Analysis of a random sample of individuals of AJ descent revealed a carrier frequency of approximately 1 in 350. Genotyping of five loci adjacent to the c.117+4A→T-containing TCIRG1 allele revealed that the presence of this mutation in the AJ population is due to a single founder. The identification of this mutation will enable population carrier testing and will facilitate the identification and treatment of individuals homozygous for this mutation.

Carrier screening of RTEL1 mutations in the Ashkenazi Jewish population.

Hoyeraal-Hreidarsson syndrome (HH) is a clinically severe variant of dyskeratosis congenita (DC), characterized by cerebellar hypoplasia, microcephaly, intrauterine growth retardation, and severe immunodeficiency in addition to features of DC. Germline mutations in the RTEL1 gene have recently been identified as causative of HH. In this study, the carrier frequency for five RTEL1 mutations that occurred in individuals of Ashkenazi Jewish descent was investigated in order to advise on including them in existing clinical mutation panels for this population. Our screening showed that the carrier frequency for c.3791G>A (p.R1264H) was higher than expected, 1% in the Ashkenazi Orthodox and 0.45% in the general Ashkenazi Jewish population. Haplotype analyses suggested the presence of a common founder. We recommend that the c.3791G>A RTEL1 mutation be considered for inclusion in carrier screening panels in the Ashkenazi population.

Carrier frequency of two BBS2 mutations in the Ashkenazi population.

Bardet-Biedl syndrome (BBS) is known to be caused by numerous mutations that occur in at least 15 of the BBS genes. As the disease follows an autosomal recessive pattern of inheritance, carrier screening can be performed for at-risk couples, but the number of potential mutation sites to screen can be daunting. Ethnic studies can help to narrow this range by highlighting mutations that are present at higher percentages in certain populations. In this article, the carrier frequency for two mutations that occur in the BBS2 gene, c.311A>C and c.1895G>C were studied in individuals of Ashkenazi Jewish descent in order to advise on including them in existing mutation panels for this population. Carrier screenings were performed on individuals from the Ashkenazi Jewish population using a combination of TaqMan genotyping assays followed by real-time polymerase chain reaction (PCR) and allelic discrimination, and allele-specific PCR confirmed by restriction analysis. The combined results indicated carrier frequencies of 0.473% (±0.0071%) for the c.311A>C mutation and 0.261% (±0.0064%) for the c.1895G>C mutation. On the basis of these frequencies, we believe that the two mutations should be considered for inclusion in screening panels for the Ashkenazi population.

[The pathogenesis of periodontal disease: a paradigm shift].

Periodontitis is a family of related diseases that differ in etiology, natural history, disease progression and response to therapy, but have a common underlying chain of events, thatareinfluenced by disease modifiers. The clinical manifestations observed are a result of the complex interplay of these factors. The pathogenesis of human periodontitis was placed on a rational footing for the first time by Page & Schroeder in 1976 and the general principles and the overall conclusions reached in that article are still largely acceptable today. Still, an enormous amount has been learned about all aspects of human periodontitis, including its pathogenesis, since 1976. A critical evaluation of the literature regarding the complex relationship between the microbial factor, the host factor and the occurrence of a disease, might be leading us over a surge of a paradigm shift in our understanding the pathogenesis of the disease. It is well acknowledged that while the etiology of periodontitis is bacterial, the pathogenesis is inflammatory. The understanding of regulation of inflammation in periodontitis is far from complete; however, as the understanding of periodontal inflammation increases, the current understanding of the microbiology of periodontitis becomes less clear. While we think we know that bacteria initiate the disease, the role of specific bacteria is still unknown. The current knowledge of the microbiology of periodontitis is based on large cross-sectional and association studies. Periodontitis is seen as the direct consequence of bacterial invasion and is regarded as an infectious disease. It is however, not possible to draw cause and- effect inferences from these studies. One might state that the inflammation precedes the overgrowth of the bacteria. In this scenario, the initiator of the disease might be early, gram-positive colonizers that elicit a profound inflammatory response in the susceptible host. The implication of that paradigm shift outlined above is that periodontitis is an inflammatory disease, and in that case the primary target of pharmacotherapy should be the inflammation, rather than the bacteria. Still, the question to be asked and investigated is whether dampening of the inflammatory response in certain individuals susceptible to periodontitis might prevent development of disease. This is a question yet to be answered.

A novel mutation in NDUFS4 causes Leigh syndrome in an Ashkenazi Jewish family.

Leigh syndrome is a neurodegenerative disorder of infancy or childhood generally due to mutations in nuclear or mitochondrial genes involved in mitochondrial energy metabolism. We performed linkage analysis in an Ashkenazi Jewish (AJ) family without consanguinity with three affected children. Linkage to microsatellite markers D5S1969 and D5S407 led to evaluation of the complex I gene NDUFS4, in which we identified a novel homozygous c.462delA mutation that disrupts the reading frame. The resulting protein lacks a cAMP-dependent protein kinase phosphorylation site required for activation of mitochondrial respiratory chain complex I. In a random sample of 5000 healthy AJ individuals, the carrier frequency of the NDUFS4 mutation c.462delA was 1 in 1000, suggesting that it should be considered in all AJ patients with Leigh syndrome.

Growth-plate chondrocytes respond to 17beta-estradiol with sex-specific increases in IP3 and intracellular calcium ion signalling via a capacitative entry mechanism.

17Beta-estradiol (E(2)) regulates growth-plate chondrocyte differentiation in a gender and cell maturation-dependent manner via classic nuclear receptors ERalpha and ERbeta, and membrane-associated signalling. Here we show that sex-specific effects of E(2) involve changes in intracellular calcium concentration (ICCC). Resting-zone chondrocytes (RC) and growth-zone chondrocytes (GC) were isolated from costochondral cartilage of male and female rats. Confluent cultures were treated with 10(-8)M E(2) or 17alpha-estradiol in the presence of high and low extracellular Ca(2+) concentration. The ICCC was determined using laser scanning confocal microscopy to measure changes in Fluo-4 fluorescence every 5s for a total of 500s. E(2) increased ICCC in the cells from female rats but had no effect on ICCC in male cells. The effect was rapid (peak at 140s) and stereospecific. E(2) increased ICCC in RC and GC chondrocytes but the effect was greater in RC cells. Low Ca(2+) media did not abolish the E(2)-dependent ICCC elevation, nor did inclusion of verapamil, which inhibits Ca(2+) channels on the cell membrane. Thapsigargin reduced the effect of E(2) on ICCC, showing that Ca(2+) pumps on the endoplasmic reticulum were involved. Pre-treatment of the cells with the ER antagonist ICI 182780 did not alter the stimulatory effect of E(2), suggesting that traditional estrogen receptor mechanisms do not play a role. E(2) caused rapid production of inositol-1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) but only in female cells, and the effect was greater in RC chondrocytes. These results indicate that E(2) regulates ICCC in a sex-specific and cell maturation state-dependent manner. The mechanism is membrane-associated and is mediated by PLC-dependent IP3 production and release of Ca(2+) from the endoplasmic reticulum.

Tay-Sachs screening in the Jewish Ashkenazi population: DNA testing is the preferred procedure.

A unique screening program for the identification of Tay-Sachs Disease (TSD) heterozygotes has been performed in the tradi- tional Orthodox Ashkenazi Jewish (AJ) community since 1983. In recent years the program has utilized the biochemical assay for the determination of hexosaminidase A levels by the heat inactivation technique as well as by direct DNA analysis. The three mutations which were analyzed were those that have been shown to be prevalent among AJ TSD patients and carriers, namely the four nucleotide insertion mutation in exon 11 (1278+TATC), the splice mutation at the 5' end of intron 12 (1421+1g-->c), and the adult mutation, a Gly(269)-->Ser substitution in exon 5 (G269S). A total of 103,133 individuals were tested by biochemical analysis, and 38,197 of them were also assayed by DNA testing. Furthermore, 151 chromosomes from TSD patients or obligate heterozygotes were subjected to DNA analysis for one of the three mutations. DNA testing of the latter identified one of the three AJ mutations in every case, predicting a very high detection rate of heterozygotes in this community by this method. By contrast, the sensitivity of the enzyme assay ranged from 93.1% to 99.1% depending on the exclusion (inclusion) of inconclusive results as positive, while the specificity ranged from 88.1% to 98.8% depending on the inclusion (exclusion) of inconclusive results as positive. Our results strongly support the use of DNA testing alone as the most cost-effective and efficient approach to carrier screening for TSD in individuals of confirmed Ashkenazi Jewish ancestry.

Familial dysautonomia is caused by mutations of the IKAP gene.

The defective gene DYS, which is responsible for familial dysautonomia (FD) and has been mapped to a 0.5-cM region on chromosome 9q31, has eluded identification. We identified and characterized the RNAs encoded by this region of chromosome 9 in cell lines derived from individuals homozygous for the major FD haplotype, and we observed that the RNA encoding the IkappaB kinase complex-associated protein (IKAP) lacks exon 20 and, as a result of a frameshift, encodes a truncated protein. Sequence analysis reveals a T-->C transition in the donor splice site of intron 20. In individuals bearing a minor FD haplotype, a missense mutation in exon 19 disrupts a consensus serine/threonine kinase phosphorylation site. This mutation results in defective phosphorylation of IKAP. These mutations were observed to be present in a random sample of Ashkenazi Jewish individuals, at approximately the predicted carrier frequency of FD. These findings demonstrate that mutations in the gene encoding IKAP are responsible for FD.

Cystic fibrosis heterozygote screening in the Orthodox Community of Ashkenazi Jews: the Dor Yesharim approach and heterozygote frequency.

In the community of the Orthodox Jews most of the marriages are arranged a screening program that is aimed at preventing the marriage of two carriers of autosomal recessive disorders is conducted by the Dor Yesharim organization. A random sample of 6,076 individuals of the Orthodox Jewish Ashkenazi community, were screened for the five mutations common in Ashkenazi patients (delta F508, W1282X, G542X, N1303K, 3849 + 10Kb C-->T). Two hundred thirty-two carriers were identified, giving a heterozygote frequency of 1:26. The relative frequencies of the individual mutations in the general population were comparable to those in the patients.

Chylous ascites as a presenting sign of prostatic adenocarcinoma.

Chylous ascites is usually associated with either primary disorders of the lymphatic system or malignancies of the lymph nodes such as Hodgkin and non-Hodgkin lymphoma. We describe, however, a young man in whom chylous ascites was a presenting sign of disseminated adenocarcinoma of the prostate gland. Most likely retroperitoneal lymph nodal replacement and tumor blockade of lymphatic collectors by metastatic adenocarcinoma was responsible for the development of chylous ascites.