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| ESHRE 2002 doc 4 |
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Risk of faulty Y chromosome transmission with ICSI –
consequences may be severe say researchers Recent advances in male infertility treatment such as ICSI mean that men with very low sperm levels now have a chance to become fathers. It's known that the sperm of some of these men may contain small deletions in the Y (male) chromosome
resulting in the male child itself being infertile.
Now, a research team led by Dr Philippos C. Patsalis from The Cyprus Institute of Neurology and Genetics in Nicosia has warned that infertility may not be the only consequence of passing on a Y chromosome with microdeletions.
In a study being presented at the ESHRE conference the researchers have linked these microdeletions to the risk of other serious conditions, including Turner's syndrome*, mixed gonadal dysgenesis**, male pseudohermaphroditism*** and, rarely, mental retardation or autism.
Recent data suggest that abnormalities in the sex chromosomes could arise when Y chromosome with a deleted AZFc gene is transmitted from one generation to
another by ICSI. Dr Patsalis said that if this hypothesis was correct it raised the possibility that some patients in whom the X and Y (female and male) chromosomes were at odds with their outward physical make-up may in fact be harbouring Y chromosome microdeletions.
They tested the hypothesis by screening 12 patients with a particular karyotype (genetic make-up) – 45,X/46,XY. All the patients had sexual ambiguities because of a lack of Y chromosome-bearing cells in the sex organs or had non-germ cell anomalies characteristic of Turner's syndrome.
A third of the cases had a complete AZFc gene deletion. In two cases the DNA of the father was available for testing. The results revealed that the deletions were new or had been present at low levels in the father.
Said Dr Patsalis: "These results highlight a potential risk for children born to fathers carrying Y chromosome microdeletions and treated by ICSI. The risk is the
development of sex chromosome aneuploidy (the loss or gain of one or two chromosomes) during foetal and embryonic development. The clinical consequences of transmitting these Y chromosome deletions can be severe."
* Turner's Syndrome: congenital disorder affecting about 1 in 3,000 females, who have one absent or abnormal X chromosome. Characteristics may include a lack of
ovarian function, short stature, cardiovascular problems, and a range of physical abnormalities.
** Gonodal dysgenesis: genetically determined failure of the testes or ovaries to produce germ cells. The most common manifestation of the condition in women is Turner's Syndrome. In men it is Klinefelter's Syndrome, which occurs in about 1 in 1,000 men, who are born with an extra X chromosome. They tend to be tall, thin and have female physical characteristics. They have normal sexual function but are sterile.
*** Pseudohermaphrodites have a physical appearance that is at variance with their gonadal sex. Females have a normal 46XX chromosome but varying degrees of
male bodily features while males have a normal 46XY chromosome but female bodily features. |
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Giovedi 23 Maggio 2013
