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Analysis of X-inactivation of blood DNA in 4-year-old girl with Lesch-Nyhan disease

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Analysis of X-inactivation of blood DNA from the affected 4-year-old girl and her parents as signified by the human androgen receptor (AR) locus.

The methylation status of the methylation-sensitive enzyme’s restriction sites near the polymorphic CAG repeat in the first exon of the AR locus correlates with X chromosome inactivation. DNA was amplified before and after HhaI digestion. The same experiment was performed using the fibroblast DNA, which was only available from the affected individual.

When the genomic DNA from the whole blood samples was amplified without HhaI digestion, two polymorphic alleles at the AR locus [AR1 (260) and AR2 (280)] were demonstrated, with the AR1 allele from the mother and the AR2 allele from the father. However, after HhaI digestion in the blood from the affected girl and the mother, only the AR1 allele could be amplified, indicating the presence of non-random X-inactivation. (Source: AlBakheet A, AlQudairy H, Alkhalifah J, Almoaily S, Kaya N, Rahbeeni Z. Detailed genetic and clinical analysis of a novel de novo variant in HPRT1: case report of a female patient from Saudi Arabia with Lesch-Nyhan syndrome. Front Genet 2023;13:1044936. Creative Commons Attribution License [CC BY], https://creativecommons.org/licenses/by/4.0.)