2008 Barcelona - European Society of Human Genetics

Cytogenetics
P02.101
case report: A case of a rare translocation of sRY region of the
Y chromosome to the short arm of the X chromosome
V. Radoi, L. Neagu, D. Mierla, D. Jardan;
Life Memorial Hospital, Bucharest, Romania.
The 46, XX karyotype male syndrome is a rare sex chromosome disorder
occurring in less then 1 in 25 000 individuals . It mostly results
from unequal crossing-over between the X and Y chromosomes during
meiosis . Here we report a two weeks old boy with bilateral cryptorchidism
and penile hypospadia . Chromosomal analysis revealed a 46, XX
karyotype and the FISH test showed the presence of the SRY region
of the Y chromosome translocated to the short arm of the X chromosome
. SRY gene located in this region is the main gene responsible
for gonadal differentiation in the male and it is essential for the normal
development of male genitalia. This report confirms the value of karyotyping
and FISH analysis in the cases of ambiguous genitalia .
P02.102
mosaicism characterization in male with 46,XX SRY positive
karyotype
O. M. Khurs, A. D. Polityko, N. V. Rumyantseva, I. V. Naumchik;
Republican Medical Center “Mother and сhild”, Minsk, Belarus.
46,XX “male syndrome” is rare chromosomal disorder in human that
occurs at about 1 in 20 000 - 25 000 males . The SRY gene, located
at p11 .3 chromosome Y, plays a key role in human sex determination
and is responsible for the reproductive system morphogenesis . Most
46,XX male individuals with normal genitalia and karyotype 46,XX are
SRY positive . This chromosomal aberration arises due to an unequal
recombination between Xp and Yp terminal region during paternal
meiosis .
Here we present a case of an infertile (azoospermia) 32 years old
male, who has normal masculinization of the external genitalia . A standard
cytogenetic study revealed the karyotype 46,XX in 25 analyzed
metaphases .
FISH analysis using LSI SRY probe Spectrum Orange (Vysis) showed
the presence of single SRY gene signal in 50 metaphases studied .
The subsequent FISH using chromosome X WCP probe Spectrum Orange
(Vysis) has demonstrated the localization of SRY signal on p-arm
of chromosome X, and constitutional karyotype abnormality was interpreted
as 46,XX .ish der(X)t(X;Y)(p22 .3;p11 .3)(SRY+) . Furthermore
the analysis of 184 metaphases has allowed to ascertain the mosaic
status of the karyotype in lymphocytes: 45,X .ish (wcpX×1)[4]/47,XXX .
ish (wcpX×3)[3]/48,XXXX .ish (wcpX×4)[1}/46,XX .ish (wcpX×2)[176] .
The results obtained demonstrate the advantage of FISH for detecting
low-grade mosaicism in patients with anomalies of sex chromosomes
.
[Supported in parts by DAAD 325/2003, DFG WER 17/01/04] .
P02.103
clinical, cytogenetic and molecular cytogenetic study of three
XX male cases
H. A. Hussein, I. I. Mazen;
National Research Centre, Cairo, Egypt.
46,XX male is a rare disorder that occurs at about 1 in 20,000 males . It
is due to accidental recombination between the short arm of the Y chromosome
and the short arm of the X in paternal meiosis .This results in
translocation of the SRY gene from the Y to the X chromosome .
Aim of this study is to report and highlight the value of cytogenetics
and (FISH) analysis for males with 46, XX Karyotype, since the phenotype
dose not always correlate with the presence or absence of Y
sequences in the genome .
In this report we present clinical, cytogenetic and molecular cytogenetic
data of three patients referred to human cytogenetics department
from Clinical genetic department . Two patients presented with infertility
with normal male external genitalia and one patient was presenting
with ambiguous genitalia . Ultrasonography revealed no müllerian derivatives
in the three patients .
Cytogenetic results for the three cases revealed 46, XX karyotype .
FISH analysis showed the presence of SRY gene on the short arm of
X chromosome in cases numbers 1& 2 and it absence in case number
3 .
Analysis of these results illustrated that combined conventional cytogenetic
and FISH techniques are essential for accurate diagnosis and
proper genetic counseling . Therefore we recommend performing molecular
cytogenetic (FISH) in cases of male infertility or male genital
ambiguity .
P02.104
A 14 bp deletion in the sry gene associated with xy sex reversal
E. Margarit 1,2 , R. Queralt 1 , M. Guitart 3 , E. Gabau 3 , R. Corripio 3 , A. Soler 1,2 , A.
Sánchez 1,2 ;
1 Biochemistry and Molecular Genetics.and IDIBAPS, Hospital Clínic, Barcelona,
Spain, 2 Centro de Investigación Biomédica en Red de Enfermedades
Raras (CIBERER), ISCIII, Barcelona, Spain, 3 Consorci Hospitalari Parc Taulí,
Sabadell, Spain.
Sex-reversed XY females can arise from different mechanisms . About
15% of the XY females with pure gonadal dysgenesis are found to
have mutations in the testicular determinant gene SRY (Sex Reversal
on chromosome Y), specially affecting the high mobility group conserved
region HMG box . The SRY gene is located at Yp11 .31 and
induces male sexual differentiation in human embryos from the 6 th
week of gestation . The failure of this process cause gonadal dysgenesis
in complete or incomplete form, depending of the presence or
not of testicular tissue remnants . Here we present a female 15 years
old with no pubertal development, hypergonadotropism, obesity and
diabetes, showing a 46,XY karyotype . The existence of the SRY gene
was confirmed by PCR. Sequencing of SRY revealed a deletion of 14
nucleotides in the coding sequence of the gene (2188delAAAGCTG-
TAACTCT), located in the 5’ region upstream of the HMG box . The
deletion of these nucleotides origins a stop codon that will give rise to a
severely truncated protein . This defective SRY protein lacks the entire
DNA-binding HMG domain and will therefore most likely be non-functional.
Only four different deletions have been previously identified in
the SRY gene (HMGD database) associated to XY sex-reversal .
P02.105
molecular analysis of SRY identifies familial and de novo
mutations in 46,XY females with different phenotypes of gonadal
dysgenesis
J. M. S. Goncalves 1 , D. Gomes 1 , J. Silva 1 , A. Parreira 1 , A. Medeira 2 , T. Kay 3 , T.
Oliveira 4 , L. Cortez 5 , J. Cidade Rodrigues 6 ;
1 Instituto Nacional de Saúde, Centro de Genética Humana, Lisbon, Portugal,
2 Serviço de Genética Médica, Hospital de Stª Maria, Lisbon, Portugal, 3 Serviço
de Genética Médica, Hospital de D Estefânia, Lisbon, Portugal, 4 Maternidade
Júlio Dinis, Porto, Portugal, 5 Serviço de Endocrinologia, Hospital Curry Cabral,
Lisbon, Portugal, 6 Hospital de Crianças Maria Pia, Porto, Portugal.
In human males, normal testicular determination is firstly triggered by
the action of the SRY protein, which is encoded by a single exon-gene
(SRY) located on Yp11 .3 . SRY has a high-mobility group (HMG) domain,
which is able to bind and bend DNA . De novo point mutations in
SRY that arise mainly in the HMG box domain, were identified in 46,XY
female patients with complete gonadal dysgenesis (CGD) . However,
even very rarely, familial SRY mutations were already described .
Here, we describe eight 46,XY female patients with mutations in the
SRY gene, seven with CGD and one with ambiguous external genitalia
. Molecular studies were performed using four sets of primers, from
nucleotides -323 to +950 of the SRY. PCR amplified DNA fragments
were analysed by SSCP or DHPLC, and subsequently sequenced
when appropriate .
In two patients with CGD, a microdeletion including all SRY coding
region was found . In the remaining six patients the following
point mutations were detected: c .53G>A(p .S18N); 89G>T(R30I);
c .169C>T(E57X); 224G>T(p .P63A) . While the last two, were not described
before, and are de novo mutations, c .53G>A(p .S18N) and
89G>T(R30I) were also found in both patient’s fathers . 89G>T(R30I)
was also detected in a first degree cousin (phenotypically nomal) of
one of the female patients with CGD . None of the above mutations
were found in more than 100 phenotypically normal unrelated males .
We evidence, that while some SRY mutations may be the cause of
complete gonadal dysgenesis, others are associated with phenotypic
heterogeneity, supporting the existence of modifier genes implicated
in sex determination .