Guillermo Alfaro

Frequency of Y chromosomal material in mexican patients with Ullrich-Turner syndrome

Cytogenetic studies have shown that 40-60% of patients with Ullrich-Turner syndrome (UTS) are 45,X, whereas the rest have structural aberrations of the X chromosome or mosaicism with a second cell line containing a structurally normal or abnormal X or Y chromosome. However, molecular analysis has demonstrated a higher proportion of mosaicism, and studies in different populations have shown an extremely variable frequency of Y mosaicism of 0-61%. We used Southern blot analysis and polymerase chain reaction (PCR) to detect the presence of Ycen, ZFY, SRY, and Yqh in 50 Mexican patients with UTS and different karyotypes to determine the origin of marker chromosomes and the presence of Y sequences. Our results indicated the origin of the marker chromosome in 1 patient and detected the presence of Y sequences in 4 45,X patients. Taken together, we found a 12% incidence of Y sequences in individuals with UTS. The amount of Y-derived material was variable, making the correlation between phenotype and molecular data difficult. Only 1 patient had a gonadoblastoma. We discuss the presence of Y chromosomes or Y sequences in patients with UTS and compare our frequency with that previously reported.

Clinical traits and molecular findings in 46,XX males

46,XX maleness is characterized by the presence of testicular development in subjects who lack a Y chromosome. The majority of affected persons have normal external genitalia, but 10–15% show various degrees of hypospadias. Several hypotheses have been proposed to explain the etiology of this constitution: translocation of the testis‐determining factor (TDF) from the Y to the X chromosome, mutation in an autosomal or X chromosomal gene which permits testicular determination in the absence of TDF, and undetected mosaicism with a Y‐bearing cell line. We report the pheno‐typic data and results of molecular analyses performed in six sporadic Mexican males with 46,XX karyotype. Molecular studies revealed Yp sequences in two individuals (ZFY+SRY+) with different phenotypes, a third one presented with a smaller segment of Yp (ZFY–SRY+) and complete virilization, while the remaining three were Y‐negative and showed hypospadias. In all subjects a hidden mosaicism with a Y‐bearing cell line was ruled out due to the absence of Y‐centromeric sequences. Our data demonstrate that the phenotype does not always correlate with the presence or absence of Y‐sequences in the genome, and confirm that 46,XX maleness is a genetically heterogeneous condition.

Molecular analysis in true hermaphrodites with different karyotypes and similar phenotypes

True hermaphroditism is characterized by the development of ovarian and testicular tissue in the same individual. Müllerian and Wolffian structures are usually present, and external genitalia are often ambiguous. The most frequent karyotype in these patients is 46,XX or various forms of mosaicism, whereas 46,XX is very rarely found. The phenotype in all these subjects is similar. We studied 10 true hermaphrodites. Six of them had a 46,XX chromosomal complement: 3 had been reared as males and 3 as females. The other 4 patients were mosaics: 3 were 46,XX/46,XY and one had a 46,XX/47,XXY karyotype. One of the 46,XX/46,XY mosaics was reared as a female, whereas the other 3 mosaics were reared as males. The sex of assignment in the 10 patients depended only on labio-scrotal differentiation. Molecular studies in 46,XX subjects documented the absence of Y centromeric sequences in all cases, arguing against hidden mosaicism. One patient presented Yp sequences (ZFY+, SRY+), which contrast with South African black 46,XX true hermaphrodites in whom no Y sequences were found. Molecular analysis in the subjects with mosaicism demonstrated the presence of Y centromeric and Yp sequences confirming the presence of a Y chromosome. Gonadal development, endocrine function, and phenotype in the 10 patients did not correlate with the presence of a Y chromosome or Y-derived sequences in the genome, confirming that true hermaphroditism is a heterogeneous condition.

Non-Hodgkin's Lymphomas in Mexico. A Clinicopathological and Molecular Analysis

It is now well established that the clinical and histopathological characteristics of non-Hodgkins lymphomas may vary significantly throughout the world. However, only a few reports have been published in Latin American countries. In this work, the clinical and pathologic findings of 264 patients with non-Hodgkins lymphomas in Mexico City were analyzed. Diffuse large (14%) and diffuse mixed cell types (20%) predominated among nodal lymphomas. Within the group of patients with high grade malignancies, immunoblastic sarcomas were the most common (40/48). It is important to mention that follicular lymphomas were sporadic (4.5%). Among extranodal lymphomas the most commonly involved site was the gastrointestinal tract (11.3%), followed by the midline (6%). Molecular analysis of 65 cases with immunoglobulin and T-cell receptor gene probes showed that most lymphomas were of B-cell lineage (66%). The remaining group was composed of T-cell (25%) and bigenotypic malignancies (9%). All attempts to establish a correlation between the clinical stage and histopathological types with the genetic findings were not successful. However, pre-B and bigenotypic lymphomas were observed mainly in patients over 60 years of age. This study highlights some relevant characteristics of non-Hodgkins lymphomas in Mexico.

DAMAGE IN B2m GENES AND DNA METHYLATION OF H-2 GENES ARE INVOLVED IN LOSS OF EXPRESSION OF CLASS I MHC PRODUCTS ON THE MEMBRANE OF LR.4, A CELL LINE DERIVATIVE OF THE T-CELL LYMPHOMA L5178Y

We have isolated an H‐2 deficient cell line (LR.4) from the T‐cell lymphoma L5178Y which grew without restrictions in the peritoneal cavity of different inbred strains of mice. The use of polyclonal anti‐H‐2 antiserum and complement indicated that LR.4 cells did not express class I determinants on the cell membrane. Southern blots of genomic DNA of LR.4 cells showed that B2m genes were severely damaged and that class I H‐2 genes were extensively methylated. Consequently, LR.4 cells failed to transcribe mRNAs for both B2m and class I H‐2 genes. On the other hand, specific immunity to LR.4 was demonstrated in C57BL/6J mice since, in subsequent challenges with either LR.4 or EL4.4, LR.4 did not grow, whereas EL4.4 grew and killed the mice. In C57BL/6J mice, rejection of LR.4 was accompanied by the production of cytotoxic antibodies. The immune response induced in C57BL/6J mice was determined by non‐H‐2 antigenic determinants in LR.4 cells.