UNSW Embryology
DEVELOPMENT OF THE REPRODUCTIVE SYSTEM
GONADOBLASTOMA; GBY
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*424500 GONADOBLASTOMA; GBYtable OF CONTENTSDatabase LinksNote: pressing the
TEXTAn increased risk for gonadoblastoma in
phenotypic females with dysgenetic gonads and the
presence of Y-chromosomal material is well
established (Verp and
Simpson, 1987). Page
(1987) postulated the existence of a gene (GBY)
on the Y chromosome with an undefined physiologic
function in normal males but with the ability to
predispose dysgenetic gonads to develop malignancy
when present in females. On the basis of 2 reported
cases of females with dysgenetic gonads, deleted Y
chromosomes, and gonadoblastoma, Page
(1987) argued that the GBY gene is located
either near the centromere or on the long arm of
the Y chromosome and is distinct from the
testis-determining factor. Petrovic
et al. (1992) described a 12-year-old girl who
was referred for chromosome analysis because of
short stature and was found to have a mosaic
karyotype 45,X/46,X,+mar. The marker chromosome was
found in 58% of the blood lymphocytes. DNA analysis
using Y-specific probes showed absence of the
testis-determining region and the presence of some
short arm and centromeric Y-chromosomal material.
In situ hybridization confirmed that the
Y-chromosomal material was associated with the
marker chromosome. At laparotomy the patient was
found to have streak gonads with a dysgerminoma
arising from a gonadoblastoma in the left gonad.
The case demonstrated that even very small
Y-derived marker chromosomes with pericentric
material can predispose the phenotypic female to
gonadal neoplasia.
Tsuchiya et al. (1995)
used sequence tagged sites to perform deletion
mapping of the Y chromosome in sex-reversed female
patients with a Y chromosome and gonadoblastoma.
The GBY gene was sublocalized to a small region
near the centromere. They estimated the size of the
GBY critical region to be approximately 1-2 Mb.
Their analysis indicated that copies of the 2
dispersed Y-linked gene families, TSPY (480100)
and YRRM (Y-chromosome RNA recognition motif;
415000)
were present in all patients. Copies of TSPY but
not YRRM fall within the GBY critical region as
formally defined by deletion mapping. Two tumor
samples showed expression of both genes and in one
patient this expression was limited to a unilateral
gonadoblastoma but absent in the contralateral
streak gonad. Although the results of Tsuchiya
et al. (1995) did not directly implicate TSPY
or YRRM in the etiology of the tumor, they raised
the issue of whether there is one GBY gene in the
critical region or possibly multiple GBY loci
dispersed on the Y chromosome.
Salo et al. (1995)
attempted to map GBY by making use of a dense map
of Y-chromosome sequence tagged sites (STSs). In 2
female patients with gonadoblastoma, small marker
chromosomes contained portions of the Y chromosome,
and a single region of overlap could be defined
extending from probe pDP97 in interval 4B, which
contains the centromere, to marker sY182 in
interval 5E of the proximal long arm. This interval
is contained in a YAC contig that comprises
approximately 4 Mb of DNA. Their result confirmed
the previous localization of GBY and greatly
refined it. The localization overlaps with the
region to which GCY (475000),
a putative growth determinant, had been assigned.
REFERENCES
CLINICAL SYNOPSIS
CREATION DATEVictor A. McKusick : 9/14/1992
EDIT HISTORYmgross : 4/8/1999 |
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