Loss-of-function mutations in HPSE2 cause the autosomal recessive urofacial syndrome

Abstract

Previously, we localized the defective gene for the urofacial syndrome (UFS) to a region on chromosome 10q24 by homozygosity mapping. We now report evidence that Heparanse 2 (HPSE2) is the culprit gene for the syndrome. Mutations with a loss of function in the Heparanase 2 (HPSE2) gene were identified in all UFS patients originating from Colombia, the United States, and France. HPSE2 encodes a 592 aa protein that contains a domain showing sequence homology to the glycosyl hydrolase motif in the heparanase (HPSE) gene, but its exact biological function has not yet been characterized. Complete loss of HPSE2 function in UFS patients suggests that HPSE2 may be important for the synergic action of muscles implicated in facial expression and urine voiding.

Figure 1

Pedigrees Used for Redefining UFS Interval and Candidate Gene Mutation Screenings Pedigrees of UFS-2, -12, -13, -14, -15, and -18 were collected from Colombia, pedigrees UFS-30 and UFS-31 were recruited from the United States, and pedigree UFS-50 was obtained from France. Patients of UFS-30 and UFS-31 share a common Irish heritage, and patients in pedigree UFS-50 are of European descent. Of note, patients in pedigrees UFS-2, -12, -13, -18, -30, -31, and -50 were from unrelated marriages, whereas patients in pedigrees UFS-14 and -15 were from consanguineous marriages.

Figure 2

Redefined UFS Interval Based on Haplotype Analysis of Patients with Recombination Events Patients II.1 of UFS-2, II.1 of UFS-13, II.1 of UFS-18, II.1 of UFS-12, IV.1 of UFS-14, and V.1 of UFS-15 were Colombian, whereas II.1 of UFS-30 was a United States patient. Markers with the homozygous genotype were boxed to define the region without recombination. Alleles for markers D10S1443 and D10S603 in patients with recombination events are in bold to show the telomeric and centromeric breakpoints, respectively. The disease interval was placed between markers D10S1433 and D10S603.

Figure 3

A Transcriptional Map for the Newly Defined UFS Disease Interval Top: a detailed genomic structure for the HPSE2 gene. Bottom: all candidate genes located between D10S1433 and D10S603. The size in genomic DNA (kb) for each transcript is shown within the figure. The order and genomic location of each microsatellite marker within the map was defined based on the genomic sequence information from the Ensemble database. The letters represent the following: A, HPSE2 (NM_021828); B, CNNM1 (NM_020348); C, GOT1 (NM_002079); D, NKX2-3 (NM_145285); E, SLC25A28 (NM_031212); F, LOC100289312 (NM_002343029); G, ENTPD7 (NM_020354); H, COX15 (NM-078470); I, CUTC (NM-015960); J, ABCC2 (NM_000392); K, DNMBP (NM_015221); L, NCRNA00093 (NR_024130); M, CPN1 (NM_001308); N, ERLIN1 (NM_006459); O, CHUK (NM_001278); P, CWF19L1 (NM_018294); Q, SNORA12 (NR_002954); R, BLOC1S2 (NM_0173809); S, PKD2L1 (NM_016112).

Figure 4

Mutations Identified in UFS Patients (A) All Colombian patients share one identical disease haplotype and carry a homozygous nonsense mutation c.1516C>T (R506X) in exon 11. (B) The United States patients possess one identical disease haplotype and carry a homozygous AA deletion (c.1465_1466delAA) in exon 10 at nucleotide positions 1465 and 1466 (start codon as position 1). (C) The French patients carry two different disease haplotypes: the first is identical to the United States patients, and the second is different from other patients. They carry a 2 bp AA deletion (c.1465_1466delAA) in exon 10, like the United States patients, and a 2 bp CT deletion (c.241_242delCT) in exon 1 at positions 241 and 242 (start codon as position 1).