Detection of SRY gene in Egyptian children with ambiguous genitalia using FISH technique

Abstract EN

-The present study was carried out for testing the presence or absence of SRY gene in 21 patients with intersex using FISH technique and LSI SRY/ CEP X dual color probes.

Based on phenotype (the appearance of the external and internal genitalia, and gonads), genotype (cytogenetic and molecular cytogenetics and pelviabdominal sonographic findings, our patients were divided into two major groups, 12 patients with male pseudohermaphroditism (57%) and 9 patients with female pseudohermaphroditism (43%).

Conventional cytogenetic study was successfully done for each patient involved in our study.

G-banding of chromosomes revealed normal male karyotype in 10 patients (10/21) (48%), normal female karyotype in 9 patients (9/21) (43%) and two cases with abnormal karyotypic findings (46,X, +mar) (patient No.

11 & 12) (2/21) (9%).

Sequential Q-banding verified one patient (No.

11) as Y-derived marker chromosome, most probably iso (Yq) with evident Q-fluorescence on both terminal ends, while the small marker chromosome seen in patient (No.

12) was clearly Q-fluorescence negative.

Subsequent FISH analysis confirmed all normal karyotypic results in both metaphase and interphase cells.

Moreover, it proved very effective in verifying the Y origin of both marker chromosomes and in localizing the site of break points and indicating the doses of SRY gene, therefore, sorting out the 2 abnormal chromosomes as idic (Y) (p11.32) (qter ( p11.32:: p11.32 ( qter) and iso (Y) (p11.1).

A low level mosaicism which is expected in cases with intersex could be missed by conventional cytogenetics due to limited number of metaphases.

Interphase FISH is a very powerful tool in detecting such cases in patients (No.

11 & 12) by detecting 45,X cell line.

FISH technique proved to be a useful ultra-rapid tool for detection of SRY gene with sure confirmatory results from both interphase and metaphase cells, therefore, enabling accurate diagnosis of patients with intersex.