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Biomedical subjects

J Zlotogora

Publications and source records attributed to J Zlotogora.

At least 37 records · Page 2Linked to original sources
PubMed1998

Germ line mosaicism.

Mosaicism in germ cells has been recognized, over the past few years, as an important and relatively frequent mechanism at the origin of genetic disorders. There are two possibilities for the existence of such a mosaicism: one is that the mutation occurs in a germ cell that continues to divide. The other possibility is that the mutation occurs very early in a somatic cell before the separation to germinal cells and is therefore present both in somatic and germinal cells. Depending on various factors, such as the gene involved and/or the degree of mosaicism, the carrier of a somatic and germline mosaicism may be asymptomatic or may present with various symptoms of the disease. There are still relatively few reports in the literature in which the origin of germ-line mosaicism has been analyzed; nevertheless, they allow for a better insight into the mechanisms involved. In some diseases, such as osteogenesis imperfecta, new mutations are often present as asymptomatic somatic and germline mosaicism in one of the parents of the propositus. In other disorders, such as neurofibromatosis, somatic mosaicism is very rare in the parents of the propositus, perhaps since such mosaicism causes clinical symptoms. These differences are particularly important for genetic counseling in order to evaluate the risk for another affected child after the birth of the propositus.

Female↗
PubMed1997

Genetic disorders among Palestinian Arabs. 2. Hydrocephalus and neural tube defects.

Congenital hydrocephalus and/or open neural tube defect was present in at least one individual of 98 families out of the 2,000 Palestinian Arabic families who have visited the Genetic clinic at the Hadassah Medical Center. In 22 families the brain malformation was part of a syndrome: Meckel syndrome in 10, Warburg syndrome in another 5, Carpenter in one, and undiagnosed in 6 families. In 76 of the families the neural tube defect and/or the hydrocephalus were non-syndromal. It seems that most of the cases of isolated non-syndromal hydrocephalus represented autosomal recessive traits and that an abnormal allele is common among Palestinian Muslim Arabs.

Abnormalities, Multiple↗
PubMed1997

Dominance and homozygosity.

Because of the high consanguinity rates in many communities in Israel we had the opportunity to study homozygosity for some dominant disorders. This experience and a review confirmed that in most cases homozygotes of dominant disorders are more severely affected than heterozygotes. In some cases molecular analysis allowed an understanding of the mechanisms involved. While heterozygosity for point mutations or deletions of PAX3 lead to similar manifestations (Waardenburg syndrome), in homozygotes the phenotype is much more severe, probably in direct relation to the loss of function. Charcot-Marie-Tooth 1A is caused by a duplication of PMP22 and further over-expression lead to a more severe disorder. In diseases in which the mutation leads to an abnormal structural protein, the homozygote may be as severely affected as the heterozygote (epidermolysis bullosa simplex) or more severely (achondroplasia, Marfan syndrome). The polyglutamine tract is translated in disorders caused by CAG triplet expansions. In homozygotes for Machado-Joseph disease the onset is earlier and the symptoms are more severe than in heterozygotes, while in Huntington disease homozygotes are affected like heterozygotes.

Achondroplasia↗
PubMed1997

Genetic disorders among Palestinian Arabs: 1. Effects of consanguinity.

Among Palestinian Arabs the rate of consanguinity is very high and some 44.3% of the marriages are between relatives (22.6% of them between first cousins). In almost 2,000 files from Palestinian Arab families who attended the genetics clinic in the Hadassah Medical Center; we were able to study the effects of consanguinity on different disorders. The consanguinity rate in families with dominant or X-linked disorders and chromosome aberrations was similar to the one observed in the general population. We did not find any significant differences in the rate of consanguineous marriages between the parents and grandparents of children affected with trisomy 21 and the general population. Thus, we were not able to confirm the suggestion that there is an increase risk for trisomies in children/grandchildren of consanguineous parents. Among the parents of patients with rare autosomal recessive disorders the consanguinity rate was much higher than the one of the general population (92.5%). Among the autosomal recessive disorders, which were relatively frequent in the population, there were fewer marriages between relatives; but in most cases the difference from rare disorders is relatively small. The importance of genetic factors in various congenital malformations, such as neural tube defects and cleft lip/palate or in various forms of infertility, was confirmed by the observation of a significantly higher consanguinity rate in the parents of these patients than is observed in the general population.

Abortion, Habitual↗
PubMed1997

Aspartylglucosaminuria among Palestinian Arabs.

Aspartylglucosaminuria (AGU) is a rare disorder of glycoprotein metabolism caused by the deficiency of the lysosomal enzyme aspartylglucosaminidase (AGA). AGU is inherited as an autosomal recessive trait and occurs with a high frequency in Finland because of a founder effect. While very few patients with AGU have been reported from non-Finnish origin, we diagnosed the disorder in 8 patients originating from 3 unrelated families, all Palestinian Arabs from the region of Jerusalem. The clinical diagnosis of AGU is often difficult, in particular early in the course of the disease, and most of the patients are diagnosed after the age of 5 years. However, since these patients excrete early large amounts of aspartylglucosamine in urine, biochemical screening is easy by urine chromatography.

Acetylglucosamine↗
PubMed1997

Two different connexin 26 mutations in an inbred kindred segregating non-syndromic recessive deafness: implications for genetic studies in isolated populations.

Non-syndromic recessive deafness (NSRD) is the most common form of prelingual hereditary hearing loss. To date, 10 autosomal NSRD loci (DFNBs) have been identified by genetic mapping; at least three times as many additional loci are expected to be identified. We have performed linkage analyses in two inter-related inbred kindreds, comprised of >50 affecteds, from a single Israeli-Arab village segregating NSRD. Genetic mapping by two-point and multi-point linkage analysis in 10 candidate regions identified the segregating gene to be on human chromosome 13q11 (DFNB1). Haplotype analysis, using eight microsatellite markers spanning 15 cM in 13q11, suggested the segregation of two different mutations in this kindred: affected individuals were homozygotes for either haplotype or compound heterozygotes. The gene for the connexin 26 gap junction protein, recently shown to be mutant in both dominant and recessive deafness, maps to this locus. We identified two distinct mutations, W77R and Gdel35, both of which likely inactivate connexin 26. The Gdel35 change likely occurs at a mutational hotspot within the connexin 26 gene. The recombination of marker alleles at the polymorphisms studied in 13q11, at known map distances from the mutations, allowed us to estimate the age of the mutations to be 3-5 generations (75-125 years). This study independently confirms the identity of connexin 26 as an NSRD gene. Importantly, we demonstrate that in small populations with high rates of consanguinity, as compared with large outbred populations, recessive mutations may have very recent origin and show allelic diversity.

Chromosomes, Human, Pair 13↗
PubMed1997

Homozygosity mapping of achromatopsia to chromosome 2 using DNA pooling.

Achromatopsia is an autosomal recessive disease of the retina, characterized clinically by an inability to distinguish colors, impaired visual acuity, nystagmus and photophobia. A genome-wide search for linkage was performed using an inbred Jewish kindred from Iran. To facilitate the genome-wide search, we utilized a DNA pooling strategy which takes advantage of the likelihood that the disease in this inbred kindred is inherited by all affected individuals from a common founder. Equal molar amounts of DNA from all affected individuals were pooled and used as the PCR template for short tandem repeat polymorphic markers (STRPs). Pooled DNA from unaffected members of the kindred was used as a control. A reduction in the number of alleles in the affected versus control pool was observed at several loci. Upon genotyping of individual family members, significant linkage was established between the disease phenotype and markers localized on chromosome 2. The highest LOD score observed was 5.4 (theta = 0). When four additional small unrelated families were genotyped, the combined peak LOD score was 8.2. Analysis of recombinant chromosomes revealed that the disease gene lies within a 30 cM interval which spans the centromere. Additional fine-mapping studies identified a region of homozygosity in all affected individuals, narrowing the region to 14 cM. A candidate gene for achromatopsia was excluded from this disease interval by radiation hybrid mapping. Linkage of achromatopsia to chromosome 2 is an essential first step in the identification of the disease-causing gene.

Chromosome Mapping↗
PubMed1997

A syndrome including thumb malformations, microcephaly, short stature, and hypogonadism.

We report on eight patients from seven different families affected with a syndrome which includes thumb defects, short stature, microcephaly, and mental retardation. Most of the patients had additional malformations, in particular amenorrhoea and azoospermia in the adults. There were no haematological manifestations and the chromosomes were normal without evidence of breakage even after stimulation. In five of the cases the probands' mother received hormonal treatment before or at the beginning of her pregnancy or both. The syndrome may be inherited as an autosomal recessive trait since the patients included both males and females and their parents were related in most cases. In addition, supporting this possibility, they all originated from a small village which may be considered as an isolate. However, in all cases but one, only one person was affected in each family and there was a significant apparent excess of healthy sibs of the probands. These observations may be the result of the variability of the syndrome or a more complex type of inheritance.

Abnormalities, Multiple↗
PubMed1997

Autosomal recessive diseases among Palestinian Arabs.

As a consequence of the high consanguinity rate among the Palestinian Arabs, many recessive disorders are present with a relatively high frequency. In a survey of 2000 different Palestinian Arab families who visited our genetic clinic, in 601 an autosomal recessive disease was diagnosed or strongly suspected. The distribution of these disorders was not uniform and some disorders, such as Krabbe disease, were found at high frequency in only a small part of the population. For some other disorders, a high prevalence was also reported among Palestinian Arabs living in other regions, for example, beta thalassaemia, Bardet-Biedl syndrome, Meckel syndrome, autosomal recessive congenital hydrocephalus, and recessive osteopetrosis. In addition, as another consequence of the high consanguinity rate, two different autosomal recessive diseases were diagnosed within the same sibship in 17 of the Palestinian Arab families.

Arabs↗
PubMed1997

The founder mutations 185delAG and 5382insC in BRCA1 and 6174delT in BRCA2 appear in 60% of ovarian cancer and 30% of early-onset breast cancer patients among Ashkenazi women.

The mutations 185delAG, 188del11, and 5382insC in the BRCA1 gene and 6174delT in the BRCA2 gene were analyzed in 199 Ashkenazi and 44 non-Ashkenazi Jewish unrelated patients with breast and/or ovarian cancer. Of the Jewish Ashkenazi women with ovarian cancer, 62% (13/21) had one of the target mutations, as did 30% (13/43) of women with breast cancer alone diagnosed before the age 40 years and 10% (15/141) of those with breast cancer diagnosed after the age 40 years. Age at ovarian cancer diagnosis was not associated with carrier status. Of 99 Ashkenazi patients with no family history of breast and/or ovarian cancer, 10% carried one of the mutations; in two of them the mutation was proved to be paternally transmitted. One non-Ashkenazi Jewish ovarian cancer patient from Iraq carried the 185delAG mutation. Individual mutation frequencies among breast cancer Ashkenazi patients were 6.7% for 185delAG, 2.2% for 5382insC, and 4.5% for 6174delT, among ovarian cancer patients; 185delAG and 6174delT were about equally common (33% and 29%, respectively), but no ovarian cancer patient carried the 5382insC. More mutations responsible for inherited breast and ovarian cancer probably remain to be found in this population, since 79% of high-incidence breast cancer families and 35% of high-incidence breast/ovarian cancer families had none of the three known founder mutations.

Adult↗
PubMed1996

Localization of two X-linked mental retardation (XLMR) genes to Xp: MRX37 gene at Xp22.31-p22.32 and a putative MRX gene on Xp22.11-p22.2.

MRX genes of 2 families with X-linked mental retardation (XLMR) were localized by linkage analysis. In family A, the gene was mapped to Xp22.31-p22.32, with significant LOD scores to various Xp22 markers within a distance of 6 Mb between DXS1223 and DXS1224. The MRX gene of this family was designated MRX37. In a mentally retarded female who is a carrier of the MRX37 gene, a random pattern of X inactivation was demonstrated. In family B, a positive LOD score, although not significant (< + 2), was found with the marker DXS1202 at Xp22.11-p22.2.

Chromosome Mapping↗
PubMed1996

[Genetic counseling for families at high cancer risk].

About 5-10% of the most common cancers, such as breast, colon and melanoma, result from mutations in inherited predisposition genes. Recently some of these genes have been mapped or even cloned. These advances in cancer genetics have made more precise genetic counseling possible for cancer patients and their families. In our clinic for specific genetic counseling 180 families with a history of cancer were seen during a 10-month period. In counseling sessions, the family history was confirmed and interpreted, personal risk was estimated and the availability of molecular genetic testing was presented. Blood samples for DNA testing were drawn from those with certain criteria who wished to be tested. Instructions for early detection were also given, depending on the personal risk of cancer as compared to that of the general population.

DNA↗
PubMed1996

Thomas syndrome: potter sequence with cleft lip/palate and cardiac anomalies.

Holzgreve et al. [Am J Med Genet 18:177-184, 1984] first reported on a syndrome including renal anomalies, heart defect, polydactyly, and cleft palate with other oropharyngeal anomalies. We report here on four sibs with renal adysplasia associated in two with cardiovascular malformations and cleft lip or cleft palate in two. We propose that these patients as the two siblings reported by Thomas et al. [Am J Med Genet 45:767-769, 1993] are affected with a syndrome different of the one described by Holzgreve et al. [Am J Med Genet 18:177-184, 1984] mainly because of the absence of polydactyly. Thomas syndrome is probably inherited as an autosomal recessive trait with marked variability.

Abnormalities, Multiple↗
PubMed1996

Characterization of two arylsulfatase A missense mutations D335V and T274M causing late infantile metachromatic leukodystrophy.

Metachromatic leukodystrophy is a lysosomal storage disorder caused by the deficiency of arylsulfatase A. We describe a novel missense mutation in exon 6 causing the substitution of Asp335 by Val. In transient transfections no enzyme activity could be expressed from the arylsulfatase A cDNA carrying this mutation. Examination of the effects of the mutation in cells stably overexpressing the mutant enzyme revealed, that the mutant enzyme is catalytically inactive and degraded in an early biosynthetic compartment. We have also investigated the effects of a previously identified mutation (T274M). The specific catalytic activity of the Met274 substituted arylsulfatase is reduced to about 35% of the normal enzyme when measured with an artificial substrate. Most of this enzyme is also degraded in an early biosynthetic compartment.

Age of Onset↗
PubMed1996

Two different mutations are responsible for Krabbe disease in the Druze and Moslem Arab populations in Israel.

Infantile Krabbe disease is a severe, fatal autosomal recessive disorder resulting from the deficiency of galactocerebrosidase (GALC) activity. It is relatively common in two separate inbred communities in Israel. In the Druze community in Northern Israel and two Moslem Arab villages located near Jerusalem the incidence of Krabbe disease is about 1 in 100-150 live births. With our cloning of the GALC gene, mutation analysis of these populations was undertaken. The Moslem Arabs were homozygous for two mutations in the GALC gene; a T-to-C transition at CDNA position 1637 (counting from the A of the initiation codon), which is considered a polymorphism and a G-to-A transition at position 1582, which changes the codon for aspartic acid to one for asparagine. The Druze patients are homozygous for a T-to-G transversion at position 1748, which changes the codon for isoleucine to one for serine. Expression studies confirmed the deleterious nature of these mutations. The development of a simple polymerase chain reaction (PCR) amplification and restriction enzyme digestion method to identify these alleles will lead to accurate carrier testing and improved genetic counseling for interested individuals in these communities.

Base Sequence↗