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N Abbas

Publications and source records attributed to N Abbas.

52 records · Page 3Linked to original sources
PubMed1992

XY sex reversal associated with a deletion 5' to the SRY "HMG box" in the testis-determining region.

The human testis-determining factor resides within a 35-kilobase (kb) region of the Y chromosome immediately adjacent to the pseudoautosomal boundary. A candidate gene for human sex determination (SRY) was isolated in this region. Here, we describe a study of 25 cases of XY females with pure gonadal dysgenesis for mutations on the Y chromosome short arm, including SRY. Southern blotting revealed a sex-reversed female harboring a deletion extending from approximately 8 kb from the pseudoautosomal boundary of the Y chromosome to at least 33 kb and no more than 60 kb upstream, toward the centromere. The deletion begins no more than 1.8 kb upstream from the first ATG of the SRY open reading frame present in the clone pY53.3. To our knowledge, no mutation has been described previously outside the SRY "HMG box" on the short arm of the Y chromosome, which is associated with sex reversal. Since the 5' extent of the SRY transcriptional unit has not been defined, the deletion may remove upstream exons of SRY and/or transcriptional regulatory motifs, either situation resulting in lack of testicular development. It cannot be formally excluded that the mutation removes a second locus, independent of SRY, that is critical for sex determination. Denaturant gradient gel electrophoresis analysis of the SRY open reading frame in the remaining 24 cases revealed de novo single base-pair transitions in the SRY conserved domain in 4 cases.

Amino Acid Sequence↗
PubMed1992

The sole presence of the testis-determining region of the Y chromosome (SRY) in 46,XX patients is associated with phenotypic variability.

Four cases of XX patients with testis development are reported. The aim of this study was to describe their clinical features and to see if there was any relationship between phenotypes and the presence of Y material. Several human Y-derived sequences including the SRY probe were used to analyze the DNA of the patients. Yp material including the pseudo-autosomal region and SRY was detected. The cases reported in this study confirm that XX true hermaphrodites cannot be distinguished from XX males on the basis of their genotypes. There is no relationship between clinical and anatomical phenotypes and the presence of Y material. SRY does not warrant a complete and normal testis differentiation. Although similar in some features with Klinefelter's syndrome patients, XX males exhibit specific clinical manifestations due to the lack of Y-specific genes.

Adolescent↗
PubMed1991

[Genetic factor of sex determination].

We have analyzed 40 cases of human XX male or XX true hermaphrodites negative for Y DNA sequences including ZFY. Among these patients we were able to demonstrate the existence of at least 3 mechanisms. 1) In one case a mosaïscism 46XY/46XX is limited to the gonad and only detected by PCR. 2) Familial cases compatible with the mutation of an autosomal (or pseudo-autosomal) down stream sex determining gene. 3) We finally observed 5 cases lacking ZFY meanwhile carrying Y specific sequences near to the pseudo-autosomal boundary, redifining the region where TDF must lie.

Animals↗
PubMed1990

A 45,X male with molecular evidence of a translocation of Y euchromatin onto chromosome 1.

A 45,X complement was found in lymphocyte and fibroblast cultures of a male infant with severe growth and mental retardation and mild dysmorphism. Lymphocyte DNA from this patient was found to contain Yp chromosome sequences. In situ hybridization (ISH) with the 50f2 probe led to a clear assignment of euchromatic material on the short arm of chromosome 1. This observation and others from the literature argue in favour of the conclusion that all 45,X males are probably either the result of undetected mosaicism or are carriers of Y translocated material.

Child, Preschool↗
PubMed1990

The impact of AIDS mortality on children's education in Kampala (Uganda).

The socioeconomic impact of the AIDS epidemic in Uganda has been evaluated through carrying out a household survey in central Kampala. A chronic disease with fever and weight loss, occurring mainly in young adult, caused about 1% mortality in 1988 in the area studied. There was a negative relation between being orphaned and access to school education. It is suggested that community-based AIDS patient care activities should put special emphasis on educational support of these children.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Y chromosome DNA polymorphisms in human populations: differences between Caucasoids and Africans detected by 49a and 49f probes.

Several Y-specific TaqI fragments are recognized by 49a and 49f probes in human male DNA digests. The occurrence of polymorphic variations in six of these fragments (A, B, C, D, F and I) has recently been reported, providing a potentially powerful tool for the study of the population genetics of the Y chromosome. The 49a-49f/TaqI polymorphisms were studied in 121 Africans (Senegal and Cameroon) and 125 Caucasians (Italy). In addition to the variability described already, four new bands were observed. Moreover, three patterns were found in which bands constantly present so far (G, O and H-P-R) were missing. At variance with previously reported findings, the coexistence of two different fragments of the same 'allelic' series (A or D) was frequently observed in the Italian sample (10.4%). For some of these 'double-banded' patterns their holoandric transmission could be demonstrated by family studies. In the light of these new findings, the hypothesis of A or D fragments being allelic forms, as advanced by the authors who first described these polymorphisms, has to be reconsidered. A total of 34 haplotypes were encountered, 22 of which are new. The Africans tested all lack C and D fragments. Moreover, about 80% of them are characterized by a band, A1, not present in the Italian group. The combination of A1C0D0 could therefore be a powerful genetic marker of paternal African ancestry. This combination occurs in five haplotypes, one of which, haplotype IV, accounts for 68% of the African sample. In contrast with the results of the mtDNA analysis on the same population samples, the degree of variability displayed by the Y chromosome sequences appears to be much lower in Africans than in Caucasians.

Africa↗
PubMedDate not supplied

A minority of 46,XX true hermaphrodites are positive for the Y-DNA sequence including SRY.

A total of 30 cases of 46,XX true hermaphroditism was analysed for Y-DNA sequences including the recently cloned gene for male testis-determination SRY. In 3 cases, a portion of the Y chromosome including SRY was present and, in 2 cases, was localised, to Xp22 by in situ hybridisation. Since previous studies have shown that the majority of XX males are generated by an X-Y chromosomal interchange, the Xp22 position of the Yp material suggests that certain cases of hermaphroditism can arise by the same meiotic event. The phenotype in the 3 SRY-positive cases may be caused by X-inactivation resulting in somatic mosaicism of testis-determining factor expression giving rise to both testicular and ovarian tissues. Autosomal or X-linked mutation(s) elsewhere in the sex-determining pathway may explain the phenotype observed in the remaining 27 SRY-negative cases.

Adolescent↗