Interferon regulatory factor 6 (IRF6) gene variants and the risk of isolated cleft lip or palate.

BACKGROUND: Cleft lip or palate (or the two in combination) is a common birth defect that results from a mixture of genetic and environmental factors. We searched for a specific genetic factor contributing to this complex trait by examining large numbers of affected patients and families and evaluating a specific candidate gene. METHODS: We identified the gene that encodes interferon regulatory factor 6 (IRF6) as a candidate gene on the basis of its involvement in an autosomal dominant form of cleft lip and palate, Van der Woude's syndrome. A single-nucleotide polymorphism in this gene results in either a valine or an isoleucine at amino acid position 274 (V274I). We carried out transmission-disequilibrium testing for V274I in 8003 individual subjects in 1968 families derived from 10 populations with ancestry in Asia, Europe, and South America, haplotype and linkage analyses, and case-control analyses, and determined the risk of cleft lip or palate that is associated with genetic variation in IRF6. RESULTS: Strong evidence of overtransmission of the valine (V) allele was found in the entire population data set (P<10(-9)); moreover, the results for some individual populations from South America and Asia were highly significant. Variation at IRF6 was responsible for 12 percent of the genetic contribution to cleft lip or palate and tripled the risk of recurrence in families that had already had one affected child. CONCLUSIONS: DNA-sequence variants associated with IRF6 are major contributors to cleft lip, with or without cleft palate. The contribution of variants in single genes to cleft lip or palate is an important consideration in genetic counseling.

Bilateral asymmetry in Chinese families with cleft lip with or without cleft palate.

OBJECTIVE: To determine if Chinese individuals with nonsyndromic cleft lip with or without cleft palate (CL/P) display more bilateral asymmetry than do their unaffected relatives. DESIGN/SUBJECTS: A case-control study of 313 individuals with CL/P from Shanghai, China, with 201 unaffected relatives as controls. METHODS: Size-adjusted asymmetry scores were defined by data on middle-finger length, palm length, palpebral fissure width, and ear length. Case-control comparisons used a multivariate repeated measures analysis of variance, paired t tests, and the Wilcoxon signed rank test. RESULTS: The ear-length measure showed a significant increase in fluctuating asymmetry (FA) in individuals with CL/P compared with their unaffected relatives, which was most pronounced in the female cleft lip and palate subgroup (p = .04). No other measures showed any increase in FA. CONCLUSION: Evidence was found for increased FA, as measured by overall ear length, in Chinese individuals with nonsyndromic CL/P, compared with their unaffected family members. The use of bilateral measurements other than dermatoglyphics may prove to be a valuable means of assessing overall developmental stability in individuals with developmental malformations and in their families.

Dermatoglyphic fingerprint heterogeneity among individuals with nonsyndromic cleft lip with or without cleft palate and their unaffected relatives in China and the Philippines.

Cleft lip with or without cleft palate (CL/P) is a common birth defect (birth prevalence ranging from 1/500 to 1/2,000) with a complex etiology. Traits potentially related to CL/P, such as dermatoglyphics, may reflect the genetic and epidemiologic heterogeneity observed in CL/P. Such phenotypic heterogeneity in dermatoglyphic patterns may account for some of the variability in previously reported associations of dermatoglyphics and CL/P. To test this hypothesis, we took dermatoglyphic prints from individuals with nonsyndromic CL/P (n = 460) and their unaffected relatives (n = 254) from the Philippines and China. For both samples three raters designated the patterns as arch, ulnar loop, radial loop, whorl, or "other." Chi-square analysis and standard ANOVA were used to investigate heterogeneity between Filipino and Chinese study subjects. The significant associations between particular pattern types and CL/P were not the same in both populations, demonstrating population-specific association of CL/P and dermatoglyphic pattern types. The ANOVA of pattern type included both CL/P cases and their relatives, with affection status, sex, and population group as variables. For each pattern type except arches, population was significant (p < 0.0001); for radial loops, affection status was additionally significant (p < 0.0001). When only CL/P cases were considered, population was again significant for the ulnar loop (p < 0.0001), whorl (p < 0.0001), and "other" (p = 0.0002) patterns. The ANOVAs demonstrate between-population heterogeneity in dermatoglyphic pattern types. These results support our hypothesis that population-specific associations and population heterogeneity in dermatoglyphic patterns exist for CL/P cases and their relatives.

Chromosome 17: gene mapping studies of cleft lip with or without cleft palate in Chinese families.

OBJECTIVE: Involvement of loci on chromosome 17, including retinoic acid receptor alpha (RARA) in nonsyndromic oral clefts has been reported in Caucasian populations, although never investigated in Asian populations. The purpose of the present study was to investigate several loci on chromosome 17, including RARA, in Chinese families. PARTICIPANTS: Thirty-six multiplex families (310 individuals), ascertained through nonsyndromic cleft lip with or without cleft palate surgical probands from hospitals in Shanghai, China, participated in the present study. There were 23 families whose probands had cleft lip and cleft palate (CLP) and 13 with cleft lip alone (CL). RESULTS: Seventeen markers, spanning chromosome 17 and about 10 cM apart were assessed. Logarithm of odds ratio (LOD) scores (two point and multipoint), model-free linkage analyses, and allelic association tests (transmission/disequilibrium, Fisher's exact tests, and chi-square) were performed on the total family sample, families with CLP probands (CLP subgroup), and families with CL probands (CL subgroup). LOD scores from the two-point analyses were inconclusive. Multipoint analyses rejected linkage except for a few regions in the CL subgroup. However, positive results were found using the model-free linkage and association methods (p < .05). The markers with positive results varied across the CL and CLP subgroups. However, the RARA region and loci nearby yielded consistently positive results. CONCLUSION: Genetic variation within the RARA locus or nearby appears to be involved in the pathogenesis of nonsyndromic oral clefts in this population. Furthermore, based on the differing pattern of results in the CL versus CLP subgroups, it appears that the formation of CL and CLP is because of either differing alleles at the same genetic locus or different but related (and/or linked) genes that modify the severity and expression of oral clefting.

Nonsyndromic cleft lip with or without cleft palate in China: assessment of candidate regions.

OBJECTIVE: Although Asians have the highest birth prevalence of oral-facial clefts, the majority of gene mapping studies of cleft lip with or without cleft palate (CL/P) have been in European or American Caucasians. Therefore, the objective of this study of Chinese families was to evaluate linkage and association between CL/P and 10 genetic markers in five chromosomal regions that have shown positive results in Caucasians. SETTING: Families were ascertained through nonsyndromic CL/P surgical probands from hospitals throughout Shanghai, China. PARTICIPANTS: Study participants included 671 individuals from 60 families with two or more members affected with oral-facial clefts. Of the 671 total individuals, 145 were affected. RESULTS: Ten markers from chromosomes 2, 4, 6, 17, and 19 were assessed (TGFA, MSX1, D4S194, D4S175, F13A1, GATA185H, D17S250, D17S579, D19S49, APOC2). LOD scores were calculated between each of the 10 markers and CL/P as well as model-free statistics of linkage (SimIBD) and association (TDT). None of the markers showed significantly positive LOD scores with CL/P. A significantly positive result (p =.01) was seen using SimIBD for APOC2 on chromosome 19, and a positive TDT result (p =.004) was obtained for D19S49, near APOC2. CONCLUSIONS: This is the first gene mapping study of CL/P in China. These results indicate that most of the genetic regions with positive results in Caucasian families may not be involved in CL/P found in China, although there is some positive evidence for the candidate region on chromosome 19.

Genome scan for loci involved in cleft lip with or without cleft palate, in Chinese multiplex families.

Cleft lip with or without cleft palate (CL/P) is a common congenital anomaly. Birth prevalences range from 1/500 to 1/1,000 and are consistently higher in Asian populations than in populations of European descent. Therefore, it is of interest to determine whether the CL/P etiological factors in Asian populations differ from those in white populations. A sample of 36 multiplex families were ascertained through probands with CL/P who were from Shanghai. This is the first reported genome-scan study of CL/P in any Asian population. Genotyping of Weber Screening Set 9 (387 short tandem-repeat polymorphisms with average spacing approximately 9 cM [range 1-19 cM]) was performed by the Mammalian Genotyping Service of Marshfield Laboratory. Presented here are the results for the 366 autosomal markers. Linkage between each marker and CL/P was assessed by two-point and multipoint LOD scores, as well as with multipoint heterogeneity LOD scores (HLODs) plus model-free identity-by-descent statistics and the multipoint NPL statistic. In addition, association was assessed via the transmission/disequilibrium test. LOD-score and HLOD calculations were performed under a range of models of inheritance of CL/P. The following regions had positive multipoint results (HLOD > or =1.0 and/or NPL P< or =.05): chromosomes 1 (90-110 cM), 2 (220-250 cM), 3 (130-150 cM), 4 (140-170 cM), 6 (70-100 cM), 18 (110 cM), and 21 (30-50 cM). The most significant multipoint linkage results (HLOD > or =2.0; alpha=0.37) were for chromosomes 3q and 4q. Associations with P< or =.05 were found for loci on chromosomes 3, 5-7, 9, 11, 12, 16, 20, and 21. The most significant association result (P=.009) was found with D16S769 (51 cM).

Meta-analysis of 13 genome scans reveals multiple cleft lip/palate genes with novel loci on 9q21 and 2q32-35.

Isolated or nonsyndromic cleft lip with or without cleft palate (CL/P) is a common birth defect with a complex etiology. A 10-cM genome scan of 388 extended multiplex families with CL/P from seven diverse populations (2,551 genotyped individuals) revealed CL/P genes in six chromosomal regions, including a novel region at 9q21 (heterogeneity LOD score [HLOD]=6.6). In addition, meta-analyses with the addition of results from 186 more families (six populations; 1,033 genotyped individuals) showed genomewide significance for 10 more regions, including another novel region at 2q32-35 (P=.0004). These are the first genomewide significant linkage results ever reported for CL/P, and they represent an unprecedented demonstration of the power of linkage analysis to detect multiple genes simultaneously for a complex disorder.