The relationship of maternal age to chromosomal abnormalities is well established; however, there have been conflicting data with regard to paternal contribution.  Of potential pertinence is that 10 – 30% of autosomal trisomies arise during paternal meiosis, 100% of XYYs and 50% of XXYs are paternal in origin, and 80% of Turner syndrome patients are missing the paternal X.  Also, an increase in paternal age is associated with the development of uniparental disomy 15, and trisomy 18 is seen with increased paternal age.  To further study the relationship of paternal age to diploidy and disomy of sperm, the authors of this paper screened human sperm using four-colour FISH probes.  Chromosomes 6, 21, X, and Y were examined to determine the incidence of disomy in sperm related to paternal age where the normal usual sperm are haploid. 

Almost 200,000 sperm were examined from 18 healthy donors, ages 24 to 74.  The investigators found a significant increase in the level of autosomal disomy and a marginally significant increase in sex chromosome disomy with increasing male age. Significant individual variation was observed.  The increase in disomy ranged from 0.3 to 17% for each 10-year period.  This suggests that older men have a tendency to show synaptic abnormalities perhaps related to the deterioration of testicular environment with advancing age.

Bosch M, et al.  Euro J  Hum Gen 2001;9:533-538.

Editor’s Comment:  There is a growing interest in paternal contributions to congenital anomalies, both potential teratogens and the effect of aging itself.  Although triploids are not usually viable, it is interesting that paternal age would seem to lead to an increased contribution to triploid conceptions.  This could also play some role in triploid-diploid mixaploid individuals.  This article is an excellent review of current knowledge pertaining to diploidy, aneuploidy, and disomy in the sperm of males of various ages and in various chromosomally determined clinical conditions.

 

Judith G. Hall, OC, MD