Cytogenetic and molecular analyses of de novo translocation dic(9;13)(p11.2;p12) in an infertile male

Genetic dosage and position effect of small supernumerary marker chromosome (sSMC) in human sperm nuclei in infertile male patient

Chromosomes occupy specific distinct areas in the nucleus of the sperm cell that may be altered in males with disrupted spermatogenesis. Here, we present alterations in the positioning of the human chromosomes 15, 18, X and Y between spermatozoa with the small supernumerary marker chromosome (sSMC; sSMC⁺) and spermatozoa with normal chromosome complement (sSMC⁻), for the first time described in the same ejaculate of an infertile, phenotypically normal male patient. Using classical and confocal fluorescent microscopy, the nuclear colocalization of chromosomes 15 and sSMC was analyzed. The molecular cytogenetic characteristics of sSMC delineated the karyotype as 47,XY,+der(15)(pter->p11.2::q11.1->q11.2::p11.2->pter)mat. Analysis of meiotic segregation showed a 1:1 ratio of sSMC⁺ to sSMC⁻ spermatozoa, while evaluation of sperm aneuploidy status indicated an increased level of chromosome 13, 18, 21 and 22 disomy, up to 7 × (2.7 − 15.1). Sperm chromatin integrity assessment did not reveal any increase in deprotamination in the patient’s sperm chromatin. Importantly, we found significant repositioning of chromosomes X and Y towards the nuclear periphery, where both chromosomes were localized in close proximity to the sSMC. This suggests the possible influence of sSMC/XY colocalization on meiotic chromosome division, resulting in abnormal chromosome segregation, and leading to male infertility in the patient.

Chromosomal Abnormalities in Infertile Men from Southern India

BACKGROUND AND OBJECTIVE

Male infertility has been associated with aneuploidies and structural chromosomal abnormalities, Yq microdeletions and specific gene mutations and/or polymorphisms. Besides genetic factors, any block in sperm delivery, endocrine disorders, testicular tumours, infectious diseases, medications, lifestyle factors and environmental toxins can also play a causative role. This study aimed to determine the constitutional karyotype in infertile males having normal female partners in a south Indian population.

MATERIALS AND METHODS

A total of 180 men with a complaint of primary infertility ranging from 1 to 25 years were screened for chromosomal abnormalities through conventional analysis of GTG-banded metaphases from cultured lymphocytes.

RESULTS

Four individuals were diagnosed to have Klinefelter syndrome. Two cases exhibited reciprocal translocations and one showed a maternally inherited insertion. Polymorphisms were seen in sixty-seven patients (37.2%).

CONCLUSION

The occurrence of chromosomal abnormalities in 4.6% and variants involving the heterochromatic regions of Y, chromosome 9 and the acrocentric chromosomes in 38.2% of the infertile men with an abnormal seminogram strongly reiterates the inclusion of routine cytogenetic testing and counselling in the diagnostic work-up prior to the use of assisted reproduction technologies.