Y Chromosome deletions and male infertility

Y chromosome analysis of infertile men and their sons conceived through intracytoplasmic sperm injection: vertical transmission of deletions and rarity of de novo deletions

OBJECTIVE

To determine the prevalence and type of Yq microdeletions in 86 consecutive men that fathered 99 sons by intracytoplasmic sperm injection (ICSI) and to determine the incidence of vertical transmission and de novo deletions in these boys.

DESIGN

Prospective clinical observational study.

SETTING

Genetics laboratory associated with a university IVF unit.

PATIENT(S)

Eighty-six consecutive infertile men presenting to an IVF clinic and their 99 ICSI-conceived sons. Fifty of the 86 men (58%) had idiopathic seminiferous tubule failure (STF); the remainder had a variety of other clinical indications for ICSI.

INTERVENTION(S)

Collection of peripheral and cord blood samples.

MAIN OUTCOME MEASURE(S)

The Yq genetic status of fathers who underwent ICSI and of their sons by the presence or absence of 22 Y-specific markers covering the four azoospermia factor (AZF) subregions.

RESULT(S)

Yq deletions of the AZFd/c region were detected in two (6.9%) of 29 azoo- or severely oligospermic men with STF. Identical deletions were found in their respective sons. No de novo deletions were detected in the remaining 97 sons conceived by men without deletions.

CONCLUSION(S)

The detection of Yq deletions only in men with severe STF is consistent with previous studies, with the AZFd/c region being most commonly affected. This study demonstrates the vertical transmission of these Yq deletions through the use of ICSI and supports the notion that, in most cases, Yq deletions will be inherited by male offspring. The absence of de novo Yq deletions in the male offspring indicates that these events are rare following ICSI in men with both STF and other common male factor indications.

Azoospermia in two Labrador retrievers

Azoospermia is described in two sibling Labrador Retriever dogs. Clinical investigations following failure to sire pups after normal matings revealed testicular hypoplasia and degeneration. Sperm were absent on repeated ejaculate examination in both dogs. Histopathological examination of testicular needle aspirate biopsy and whole testicle of the first dog displayed an absence of spermatids and spermatocytes. Seminiferous tubules containing Sertoli cells with or without primary spermatogonia were present in the second dog. Peritubular lymphocyte accumulation was also present in both dogs. The dogs had been conceived using frozen-thawed semen.

Chromosome translocations in couples with in-vitro fertilization implantation failure

Recurrent miscarriage is known to be associated with parental chromosomal abnormalities, particularly balanced reciprocal and Robertsonian translocations. The aim of this study was to test the hypothesis that couples with in-vitro fertilization (IVF) implantation failure, like those with recurrent miscarriage, have a higher than expected prevalence of translocations which may impact on pregnancy outcome. Patients who previously had at least 10 embryos transferred without achieving clinical pregnancy were evaluated for chromosome abnormalities as part of screening investigations for implantation failure. Recurrent miscarriage patients with a history of at least three consecutive first-trimester abortions were also tested. Results were compared to reports of infertility patients presenting for treatment and population neonatal screening programmes. Chromosomal abnormalities overall were detected in 13/514 individuals with implantation failure (2.5%), and 15/319 individuals with recurrent miscarriage (4. 7%). Translocations (reciprocal and Robertsonian) were found in 7/514 individuals (1.4%) and 7/219 couples (3.2%) with implantation failure (P < 0.0005 compared with infertile controls and P < 0.0001 compared with screened neonates). Translocations were found in 13/319 individuals (4.1%) and 12/130 couples (9.2%) with recurrent miscarriage. Balanced parental translocations may be implicated in the pathogenesis of IVF-implantation failure. Genetic evaluation should be considered as part of the investigation of these patients.

Genetics and human reproduction

Most people want children, and most people want healthy children. For those couples with an infertility problem who have recourse to assisted reproduction, usually in vitro fertilization (IVF) or donor insemination (DI), the practitioners have a special responsibility to ensure as far as possible that the babies in whose conception they assist are in good health. How can they best tackle the challenge of inherited diseases, of which about 4000 are known today, and chromosomal malfunction?