Molecular characterization of a Y-derived marker chromosome and identification of indels in the DYS1 region in a patient with stigmata of Turner syndrome

Abstract

Presence of the Y chromosome in human female and its absence in the male is an abnormal condition, implying a spectrum of genetic abnormalities. In this communication, we describe studies conducted on a 17-year-old patient (HK-459) with stigmata of Turner syndrome. We analysed the hormonal profile of the subject, chromosomal constitution and DNA for the five different loci encompassing both the arms of the Y chromosome. Chromosomal analysis showed mosaicism containing 45,X/46,X,+mar but no Y chromosome. The X chromosome and all the autosomes of the patient and her parents were normal. The Southern analysis of the patient's genomic DNA with probes specific to DYZ1 locus did not detect the corresponding Y-specific signal. Similarly, primers RG4, RG7 and PABY, corresponding to SRY gene and pseudoautosomal boundary regions respectively, failed to generate Y-specific amplicons. However, primers DYZ3 and DYS1, representing centromeric heterochromatic and euchromatic regions respectively, on the long arm of the Y chromosome uncovered Y-specific signals in the patient and her mother. Sequence analysis of DYS1-specific (710 bp) amplicon from the patient, both of her parents and two normal males showed insertion/deletion mutation in the patient. It is inferred that the Y-derived marker chromosome in the patient is of maternal origin and had undergone post-zygotic mutational events. The possible prognostic implications of this combined approach in the patient(s) with stigmata of Turner syndrome are discussed here.