Leydig cell hypoplasia due to inactivation of luteinizing hormone receptor by a novel homozygous nonsense truncation mutation in the seventh transmembrane domain.

Inactivating mutations in the LH receptor are the predominant cause for male pseudohermaphroditism in subjects with Leydig cell hypoplasia (LCH). The severity of the mutations, correlates with residual receptor activities. Here, we detail the clinical presentation of one subject with complete male pseudohermaphroditism and LCH. We identify within the proband and her similarly afflicted sibling a homozygous T to G transversion at nucleotide 1836 in exon 11 of the LH/CGR gene. This causes conversion of a tyrosine codon into a stop codon at codon 612 in the seventh transmembrane domain, resulting in a truncated receptor that lacks a cytoplasmic tail. In vitro, in contrast to cells expressing a normal LHR, cells transfected with the mutant cDNA exhibit neither surface binding of radiolabeled hCG nor cAMP generation. In vitro expression under the control of the LHR signal peptide of either a wild type or mutant LHR-GFP fusion protein shows no differences in receptor cellular localization. In conclusion, the in vitro studies suggest that residues in the seventh transmembrane domain and cytoplasmic tail are important for receptor binding and activation without playing a major role in receptor cellular trafficking.

Familial complex chromosome rearrangement giving rise to balanced and unbalanced recombination products.

We report on a family ascertained through a 14-month-old girl with a terminal deletion of chromosome 8p23.1. Analysis of the karyotype of other relatives showed that the mother is the carrier of a balanced complex 4-break chromosome rearrangement, which she and her brother inherited from their father following recombination. This complex chromosome rearrangement (CCR) was confirmed by fluorescence in-situ hybridization (FISH) using libraries for chromosomes 1, 8, and 9, and telomeric probes for the long arm of chromosome 9. The karyotype of the maternal grandfather was 46,XY,t(1;8) (p31;q21.1),t(8;9) (p23.1;q34). The karyotype of his daughter is 46,XX,rec(8)t(1;8) (p31;q21.1)t(8;9)(p23.1;q34)pat. The karyotype of the proposita is 46,XX,rec(8)t(8;9) (p23.1;q34)mat, and that of her abnormal elder sister is 46,XX,t(1;8)(p31;q21.1)rec(8) t(8;9) (p23.1;q34)mat,der(9)t(8;9) (p23.1;q34) mat. Unbalanced segregation and/or recombination during maternal meiosis gave rise to the two abnormal sisters, one effectively with 8p trisomy and the other with monosomy for that same 8p segment. To our knowledge, this is the first case of a familial CCR giving rise to unbalanced recombination products.

Chromosome 10p11.2-p12.2 duplication: report of a patient and review of the literature.

We report on a young male with mental retardation, slightly upslanting palpebral fissures, strabismus, high-arched palate, retrognathia, and flat feet. Cytogenetic analysis in addition to fluorescent in situ hybridization (FISH) and comparative genomic hybridization (CGH) showed the presence of a chromosome 10p11.2-->p12.2 duplication. Karyotypes of the parents were normal. Comparison of the clinical findings observed in the present patient with those observed in other reported cases with duplication 10p suggest that the presence of high arched/cleft palate and retrognathia may be related to the 10p11.2-->p12.2 duplication. Also, no critical region for the trisomy 10p syndrome has been delimited.

Trisomy 22 and facioauriculovertebral (Goldenhar) sequence.

We report on an infant girl born with complete trisomy 22 and left hemifacial microsomia, ear anomaly, and limbal and epibulbar complex choristoma. Trisomy 22 was confirmed by prometaphase chromosome analysis and in situ hybridization. This patient extends the list of chromosome abnormalities associated with apparent Golenhar sequence and emphasizes the importance of chromosome analysis in the investigation of patients with this condition. A detailed ophthalmopathological investigation is reported.

Recurrent molar pregnancies in a family with extensive intermarriage: report of a family and review of the literature.

BACKGROUND: Familial recurrent molar pregnancies are exceedingly rare. The genetic basis for recurrent moles is not well understood, and its association with major human lymphocytic antigen histocompatibility is debatable. The purpose of this report is to present a family with extensive intermarriage and recurrent molar pregnancies with some emphasis on the result of the human lymphocytic antigen-typing. CASE: Two sisters, both married to first-degree cousins, had three and five pathologically confirmed molar pregnancies, respectively. A second-degree cousin, also married to her first-degree cousin, is also reported to have had five consecutive moles. Chromosomal analysis and human lymphocytic antigen-typing on the two sisters and their spouses was performed. Human lymphocytic antigen-typing was compared to a cross-sectional sample of our population. This showed a high incidence of unusual human lymphocytic antigens in these family members. CONCLUSION: In families with extensive intermarriage and recurrent molar pregnancies, patients and their spouses may have unusual human lymphocytic antigen histocompatibility, which supports the possibility of a strong genetic predisposition expressed at the level of major histocompatibility class I and II gene translation.

Karyotype analysis in chronic myelogenous leukemia. A three-year experience at the American University of Beirut Medical Center (AUBMC).

We report the results of karyotype analysis on cases referred to our laboratory for chronic myelogenous leukemia (CML) over a period of three years. A total of 68 patient were referred and a karyotype was successfully obtained in all cases except one. Thirty-one percent of cases were found to have a normal karyotype, 58.5% were Philadelphia (Ph1) positive while 10.5% of cases had chromosome abnormalities other than Ph1. Among the Ph1 positive cases, 92% had the standard translocation (9;22), 7.7% had a variant translocation and 12.8% had additional chromosome abnormalities. Our results are compared to those generally reported in the literature and the comparisons are discussed.

[Retrospective study of nine Lebanese families with fragile X syndrome and review of the literature]. / Etude retrospective de 9 familles libanaises atteintes du syndrome de l'X fragile et revue de la litterature.

The Fragile X syndrome is the most common inherited form of mental retardation. Despite its incidence, which is estimated at 1/4000 boys, only 9 families have been documented so far in Lebanon, of which 3 have been partially investigated. This syndrome therefore seems to be largely ignored by physicians. Although no treatment is yet available for the Fragile X syndrome, the diagnosis of the disorder in a child is essential in order to provide the family with genetic counselling. The most critical point is still to convince the family of the need for such an evaluation and relieve the parents of any feeling of guilt.

Karyotype of amniotic fluid cells at the AUB-MC results on 2000 cases.

We report results on 2000 cases of amniotic fluid referred for karyotype analysis. Referrals were advanced maternal age in 64% of cases and abnormal ultrasound in 12% of cases. The frequency of chromosome aneuploidy was 2.4% in the first category and that of chromosome abnormalities 8% in the second. The incidence of marker chromosomes was 0.25%, that of mosaicism 0.3%, and maternal cell contamination was observed in 0.6% of cases. The overall culture failure rate was 0.9%. Our results are mostly in accordance with figures from larger surveys, published in the literature and differences might be due to the smaller number of samples in this series and variation in referral and/or sampling protocols.

Constitutional chromosome abnormalities among patients referred for blood karyotype analysis: a 5-year study at the AUBMC.

We report results on 2010 cases of blood referred for constitutional karyotype analysis. Referrals were grouped into 16 different categories, of which reproductive failure represented the highest percentage (33%), followed by structural congenital abnormalities (14.17%), developmental delay (11.34%), Down syndrome (9.65%), and abnormal sexual development (8.16%), while other categories represented smaller percentages. The total rate of abnormality was 16%, and the highest abnormality rates were among the clinically-recognizable chromosomal syndromes, while lower percentages were detected among less specific referrals. However, abnormality rates were generally different from the typical reported rates, probably due to the inclusion of cases not requiring chromosome analysis or the failure to recognize specific chromosomal syndromes. Other identified problems included lack of proper phenotypic description and difficulty in obtaining familial follow-up for proper diagnosis and genetic counseling.

Effect of age, gender and calciotropic hormones on the relationship between vitamin D receptor gene polymorphisms and bone mineral density.

BACKGROUND/OBJECTIVES: Hypovitaminosis D is a major public health problem worldwide and unexpectedly more so in sunny countries. Vitamin D receptor (VDR) gene is associated with inter-individual variance in bone mineral density (BMD). Studies assessing the effect of VDR gene polymorphisms on BMD yielded conflicting results. The aim of this study was to assess the relationship between VDR polymorphisms and BMD in the Lebanese, across age groups and genders and to assess the effect of PTH and lean mass and vitamin D levels on such relationship. SUBJECTS/METHODS: In total, 203 subjects aged 65-85 years and 336 children aged 10-17 years. Polymorphisms in the VDR gene were assessed with the restriction enzymes BsmI, TaqI and ApaI. Bone mineral content, BMD and lean mass were measured using Dual-Energy X-ray Absorptiometry (DXA). The dominant hand strength was measured in children. RESULTS: Heterozygote genotype was the most frequent in both age groups. There was no difference in the frequency distribution of genotypes between the young and the elderly. No relationship between VDR genotypes and lean mass was found in either age group. Heterozygote boys had the lowest parathormone (PTH) and heterozygote elderly women had the highest BMD at the spine and forearm. CONCLUSIONS: In the Lebanese, the relationship between VDR polymorphisms and BMD differs by age. Survival does not seem to differ by VDR genotype. However, further studies are needed to assess the effect of VDR gene polymorphisms on mortality per se and time to mortality, not evaluated in this study.

A cytogenetic register of down syndrome in Lebanon.

OBJECTIVES: To provide data on the cytogenetics and epidemiology of Down syndrome in our community. METHODS: All cases of Down syndrome diagnosed cytogenetically were entered over a period of 5 years together with data regarding age at referral, parental ages and parity. RESULTS: A total of 280 cases were entered. In postnatal cases, the mean maternal age was 32.19 years and 41.5% of mothers were over 35 years. Only 47.3% of Down syndrome children were diagnosed at less than 1 month of age. The male to female sex ratio of 1.66 is significantly more elevated than that reported in larger registers. CONCLUSIONS: Because of problems inherent to Lebanon, this register does not have a high level of ascertainment, however it appears that the emphasis in a potential prevention programme should be placed on education, information and family planning.

Acceptance of first-trimester prenatal diagnosis for the haemoglobinopathies in Lebanon.

We have interviewed 83 couples at risk for a haemoglobin disorder, mostly beta-thalassaemia, in an effort to evaluate their attitude towards first-trimester prenatal diagnosis. Most of the families had received poor education and were of low socio-economic status and more than half of the couples were not properly aware of their genetic risk. Fifty-nine per cent of the couples were definitely in favour of prenatal diagnosis, 23 per cent were uncertain at the time of the interview, and 18 per cent were opposed to such testing, because of their religious conviction against termination of a pregnancy. Another important factor which seems to influence choice was the cost of the test. Essential issues that arise from this study include the importance of a control programme adapted to particular populations, proper information and counselling, and the need for financial support in countries such as Lebanon.

Attitudes towards prenatal diagnosis and termination of pregnancy among health professionals in Lebanon.

OBJECTIVES: To assess the attitudes of health professionals in Lebanon towards prenatal diagnosis and termination of pregnancy, for a series of genetic, non-genetic and non-medical conditions. METHODS: A total of 158 questionnaires were sent to geneticists, family doctors, pediatricians and obstetricians/gynecologists, that included information on sociodemographic variables and sets of questions and case scenarios, to which participants were asked to reply anonymously. RESULTS: Responses from the 75 participants revealed that the type of specialty did not significantly influence their attitude. However, acceptance of termination of pregnancy was influenced by gender, age, marital status, religion and its importance in their daily life. In general, acceptance of termination of pregnancy in the case of mild or severe clinical conditions was comparable to that reported from European countries, but more favorable in the case of sex chromosome abnormalities. Acceptance of prenatal diagnosis for non-clinical conditions was, however, lower than that reported in Western nations. CONCLUSION: The study provides a good basis for further studies with a larger number of respondents representing various geographical regions of the country.

Cell cycle studies in chorionic villi.

We have studied the cell cycle of cells obtained from chorionic villi in direct and culture preparations by incorporation of the thymidine analogue BrdU to produce late-labelling or sister chromatid differentiation patterns. We have, therefore, been able to estimate the duration of the cell cycle and, more specifically, the length of some of its phases. While results for chorionic villus sample cells in culture resembled those obtained for fibroblasts, data for the spontaneously dividing trophoblastic cells in direct preparations were different. Villi exposed to BrdU immediately after sampling showed a slight delay in the incorporation of the analogue and a lower percentage of labelled cells compared to villi treated after an overnight incubation, probably due to a temporary effect of the sampling technique. Results from semi-direct protocols suggest that cells have a G2 of no more than 4 h, and a mid-S phase of 10-16 h. The G1 period is very variable. After 48 h incubation with BrdU, only 4% of cells reach their second generation, whereas this percentage increases up to 70% after 72 h, indicating that under these experimental conditions most cells have a cell cycle of approximately 36 h. The average number of sister chromatid exchanges was similar in both direct preparations and cultures: 5.2 +/- 2.1 SCE per cell.

Molecular characterization of a mouse Y chromosomal repetitive sequence amplified in distantly related species in the genus Mus.

This report describes a 1.1 kb long mouse Y chromosomal sequence designated 142-4. It has a 42% GC content and is rich in short direct and inverted repeats. 142-4 related sequences are repeated about 200 times in the Mus musculus Y chromosome and their distribution was visualized by in situ hybridization. 142-4 detected a restriction fragment length polymorphism that differentiated between the M. m. musculus type and the M. m. domesticus type Y chromosome. Southern blot analysis of DNAs isolated from a panel of mouse species showed that 142-4 related sequences were amplified in the Y chromosomes of M. minutoides, M. musculus, M. saxicola, M. spicilegus, and M. spretus but not in those of M. caroli, M. cookii, and M. pahari. These results suggest that 142-4 related sequences are evolutionarily unstable and their accumulation patterns do not correlate with the known phylogenetic relationships of mouse species in the genus Mus.

Ring chromosome 18q and jumping translocation 18p in an adult male with hypergonadotrophic hypogonadism.

Constitutional jumping translocations (JT) are rare, especially in phenotypically normal individuals. We report on an adult male with partial hypogonadism as the sole phenotypic abnormality with an unusual chromosome abnormality. In this patient, centric fission of chromosome 18 lead to formation of a ring 18q chromosome, while 18p formed a JT through centromere-telomere fusion with chromosome 8q (66%) or 20q (13%). In 21% of cells, the 18p fragment was missing. Fluorescent in situ hybridization revealed the presence of interstitial telomeres at the junction site of the fusion and unequal distribution of the alphoid sequences through the centric fission, leaving a small, yet functional centromere within the ring. We discuss the phenotype of the patient in light of this unusual karyotype.

The application of automated metaphase scanning to direct preparations of chorionic villi.

In order to increase the speed of analysis of metaphases from chorionic villi direct preparations, we have investigated the use of two automatic scanning devices, the Magiscan II and a version of Metafip (the research laboratory precursor of Cytoscan). The speed, efficiency, and ranking system have been compared to manual scanning. Results show that both machines detect approximately 80 per cent of the total analysable metaphases detected by a trained cytogeneticist. There appears to be reasonable agreement in ranking between methods.

In situ hybridization studies for the detection of common aneuploidies in CVS.

We have attempted to evaluate the efficiency of interphase cytogenetics in the detection of specific aneuploidies in chorionic villus samples. For this purpose, we used alphoid repetitive sequences specific for the chromosomes involved in the common aneuploidies, namely probes for chromosomes 13, 18, 21, X, and Y. These probes were applied to normal and abnormal CVS cases, as well as to a few mosaic cases. Results from these preliminary studies indicate that the technique can be very efficient for the detection of specific aneuploidies and can be particularly useful in the analysis of mosaic cases, which usually requires the screening of a high number of metaphases.

Beta-thalassemia mutations and haplotype analysis in Lebanon.

The molecular basis of beta-thalassemia in Lebanon reflects the heterogeneity of the Lebanese population. Eighteen different mutations were identified among a total of 277 chromosomes. There is evidence of clustering of some mutations in particular geographic regions or among specific religious groups. Haplotype analysis, using seven restriction sites was performed on a total of 110 samples and 11 different haplotypes were identified. The five most common mutations were each found on two different haplotypes, and most linkages were as previously reported in other Mediterranean populations, with a few exceptions, also showing some clustering.