A novel large deletion encompassing the whole of the galactose-1-phosphate uridyltransferase (GALT) gene and extending into the adjacent interleukin 11 receptor alpha (IL11RA) gene causes classic galactosemia associated with additional phenotypic abnormalities

Abstract

Objective The characterization of a novel large deletion in the galactose-1-phosphate uridyltransferase (GALT) gene accounting for the majority of disease alleles in Cypriot patients with classic galactosemia. Methods DNA sequencing was used to identify the mutations followed by multiplex ligation-dependent probe amplification (MLPA) analysis in the cases suspected of harboring a deletion. In order to map the breakpoints of the novel deletion, a PCR walking approach was employed. A simple PCR assay was validated for diagnostic testing for the new deletion. Haplotype analysis was performed using microsatellite markers in the chromosomal region 9p. RT-PCR was used to study RNA expression in lymphoblastoid cell lines. Results The new deletion spans a region of 8489 bp and eliminates all GALT exons as well as the non-translated sequences of the adjacent interleukin 11 receptor alpha (IL11RA) gene. In addition, the deletion is flanked by a 6 bp block of homologous sequence on either side suggesting that a single deletion event has occurred, probably mediated by a recombination mechanism. Microsatellite marker analysis revealed the existence of a common haplotype. The RNA expression studies showed a lack of IL11RA transcripts in patients homozygous for the deletion. Conclusions We have identified and characterized a novel contiguous deletion which affects both the GALT enzyme and the IL11RA protein resulting in classic galactosemia with additional phenotypic abnormalities such as craniosynostosis, a feature that has been associated with defects in the IL11RA gene.