Investigation of the W185X nonsense mutation of PVRL1 gene in Italian nonsyndromic cleft lip and palate patients

Nonsyndromic cleft lip with or without cleft palate (CL/P; MIM 119530), a common birth defect, is a genetically complex trait. Several genetic and environmental factors seem to be involved in the development of this malformation [Carinci et al., 2003]. Nevertheless, CL/P also occurs as a part of many single gene syndromes, and some of these genes may also have roles in nonsyndromic CL/P. Suzuki et al. [2000] showed that the rare autosomal recessive syndrome CL/P-ectodermal dysplasia (CLPED1; MIM 225060) is caused by the loss-of-function of PVRL1 gene, which encodes nectin-1, a cell-to-cell adhesion molecule. The same group demonstrated that heterozygosity of the nonsense mutation W185X is a genetic risk factor for nonsyndromic CL/P in northern Venezuela [Sozen et al., 2001]. To verify whether the W185X mutation is a genetic risk factor for nonsyndromic CL/P in the Italian population, 71 familial CL/P belonging to 71 different pedigrees, 75 sporadic CL/P, and 100 unrelated unaffected individuals were enrolled in this study. The W185X mutation is a singlenucleotide change G!A that creates a StyI restriction endonuclease site. Therefore, a 160 bp segment of the exon 3 containing the mutation was amplified by PCR using the following primers: W185X.for 50CCACCAATTGGATAGAGGGTA30 and W185X.rev 50CGGATCTCCTGGTACTCTGC30. Amplimers were digested with StyI restriction endonuclease, electrophoresed on 2.5% agarose gel, and visualized by ethidium bromide. Positive controls, containing the mutation generated by site-directed mutagenesis (www.buckinstitute. org/benz/prot/prot12.htm), were included to verify the assay efficiency in each test. Of the 146 CL/P patients and of the 100 unaffected individuals analyzed in this study for the presence of the W185X mutation in the PVRL1 exon 3, none was positive. The results of this investigation indicate that in Italy the W185X mutation is not common and in turn, it does not constitute a risk factor for nonsyndromic CL/P. As suggested by Suzuki et al. [2000], since the PVRL1 gene product constitutes a receptor for herpesviruses, in the Margarita Island population the mutation may be selected positively for an increased resistance to infections of the carriers. Our findings significantly differ from those previously observed in the Venezuelan population [Sozen et al., 2001]. This discrepancy likely reflects the complex etiology of the CL/P malformation. Indeed, the numerous genetic and environmental factors involved probably contribute differently to the development of the malformation in distinct populations.