Assignment of the locus for ichthyosis prematurity syndrome to chromosome 9q33.3–34.13

Autosomal recessive congenital ichthyosis (ARCI) is a clinically and genetically heterogeneous group of inherited disorders of keratinisation, with an estimated incidence of one per 200 000 newborns.1 In Scandinavia, the prevalence is closer to one in 50 000.2,3 By electron microscopy, ARCI can be classified into four subgroups—ichthyosis congenita I–IV—and one so far undefined group. Six loci have been associated with ARCI: on chromosomes 2q34 (LI2 (MIM 601277)), 3p21 (NCIE2 (MIM 604780)), 14q11.2 (LI1 (MIM 242300) and NCIE1 (MIM 242100)), 17p13.1 (LI5 (MIM 606545)), 19p12–q12 (LI3 (MIM 190195)), and 19p13.1–p13.2 (NNCI (MIM 604781)).4–9 Genes that correspond to four of these have been identified: the transglutaminase 1 gene ( TGM1 (MIM 190195)) on chromosome 14q11, the comparative gene identification 58 ( CGI-58 (MIM 604780)) on chromosome 3p21, two genes from the lipoxygenase (LOX) family—lipoxygenase-3 ( ALOX3 ) and 12(R)-lipoxygenase ( ALOX12B (MIM 603741))—on chromosome 17p13.1, and, most recently, the adenosine triphosphate binding cassette 12A ( ABCA12A (MIM 607800)) on chromosome 2q34.10–14 The transglutaminase 1 protein takes part in the formation of the lipid envelope on the surface of epidermal keratinocytes. Cells with a disrupted TGM1 gene have a defective epidermal barrier function. TGM1 is altered in one third of patients with ichthyosis congenita type I and all patients with ichthyosis congenita type II.2,12,15,16 Mutations in the CGI-58 gene on chromosome 3p21 cause Chanarin-Dorfman disease (CDS (MIM 275630)). The protein CGI-58 belongs to a large family of proteins characterised by an α/β hydrolase fold and contains three sequence motifs found in the esterase, lipase, and thioesterase subfamily. Affected patients have raised levels of triacylglycerol, and CGI-58 has been postulated to be involved in recycling of triacylglycerol derived monoacylglycerol or diacylglycerol to specific phospholipids or in the catabolism of long chain fatty acids.11 Mutations in either of …