Vincent Yeow

A genome-wide association study of cleft lip with and without cleft palate identifies risk variants near MAFB and ABCA4

Case-parent trios were used in a genome-wide association study of cleft lip with and without cleft palate. SNPs near two genes not previously associated with cleft lip with and without cleft palate (MAFB, most significant SNP rs13041247, with odds ratio (OR) per minor allele = 0.704, 95% CI 0.635–0.778, P = 1.44 × 10−11; and ABCA4, most significant SNP rs560426, with OR = 1.432, 95% CI 1.292–1.587, P = 5.01 × 10−12) and two previously identified regions (at chromosome 8q24 and IRF6) attained genome-wide significance. Stratifying trios into European and Asian ancestry groups revealed differences in statistical significance, although estimated effect sizes remained similar. Replication studies from several populations showed confirming evidence, with families of European ancestry giving stronger evidence for markers in 8q24, whereas Asian families showed stronger evidence for association with MAFB and ABCA4. Expression studies support a role for MAFB in palatal development.

Evidence for gene-environment interaction in a genome wide study of nonsyndromic cleft palate.

Nonsyndromic cleft palate (CP) is a common birth defect with a complex and heterogeneous etiology involving both genetic and environmental risk factors. We conducted a genome‐wide association study (GWAS) using 550 case‐parent trios, ascertained through a CP case collected in an international consortium. Family‐based association tests of single nucleotide polymorphisms (SNP) and three common maternal exposures (maternal smoking, alcohol consumption, and multivitamin supplementation) were used in a combined 2 df test for gene (G) and gene‐environment (G × E) interaction simultaneously, plus a separate 1 df test for G × E interaction alone. Conditional logistic regression models were used to estimate effects on risk to exposed and unexposed children. While no SNP achieved genome‐wide significance when considered alone, markers in several genes attained or approached genome‐wide significance when G × E interaction was included. Among these, MLLT3 and SMC2 on chromosome 9 showed multiple SNPs resulting in an increased risk if the mother consumed alcohol during the peri‐conceptual period (3 months prior to conception through the first trimester). TBK1 on chr. 12 and ZNF236 on chr. 18 showed multiple SNPs associated with higher risk of CP in the presence of maternal smoking. Additional evidence of reduced risk due to G × E interaction in the presence of multivitamin supplementation was observed for SNPs in BAALC on chr. 8. These results emphasize the need to consider G × E interaction when searching for genes influencing risk to complex and heterogeneous disorders, such as nonsyndromic CP. Genet. Epidemiol. 2011.  © 2011 Wiley‐Liss, Inc. 35: 469‐478, 2011

Association between IRF6 and nonsyndromic cleft lip with or without cleft palate in four populations

Purpose: The interferon regulatory factor 6 (IRF6), the gene that causes van der Woude syndrome has been shown to be associated with nonsyndromic cleft lip with or without palate in several populations. This study aimed to confirm the contribution of IRF6 to cleft lip with or without palate risk in additional Asian populations.Methods: A set of 13 single nucleotide polymorphisms was tested for association with cleft lip with or without palate in 77 European American, 146 Taiwanese, 34 Singaporean, and 40 Korean case-parent trios using both the transmission disequilibrium test and conditional logistic regression models.Results: Evidence of linkage and association was observed among all four populations; and two specific haplotypes [GC composed of rs2235373-rs2235371 (p.V274I) and AAG of rs599021-rs2235373-rs595918] showed the most significant over- and undertransmission among Taiwanese cases (P = 9 × 10−6 and P = 5 × 10−6, respectively). The AGC/CGC diplotype composed of rs599021-rs2235373-rs2013162 showed almost a 7-fold increase in risk among the Taiwanese sample (P < 10−3). These results confirmed the contribution of this gene to susceptibility of oral clefts across different populations; however, the specific single nucleotide polymorphisms showing statistical significance differed among ethnic groups.Conclusion: The high-risk genotypes and diplotypes identified here may provide a better understanding of the etiological role of this gene in oral clefts and potential options for genetic counseling.

The use of nasal splints in the primary management of unilateral cleft nasal deformity.

Primary surgical correction of the cleft lip nasal deformity is routinely performed at the Craniofacial Center at Chang Gung Memorial Hospital. Over time, however, there is a tendency for the lower lateral cartilage to retain its memory and, subsequently, recreate the preoperative nasal deformity. Therefore, it is current practice to use a nostril retainer for a period of at least 6 months to maintain the corrected position of the nose. The aim of this study was to qualitatively assess the benefit of postoperative nasal splinting in the primary management of unilateral cleft nasal deformity. Data from two groups of 30 patients with complete unilateral cleft lips each were retrospectively collected and analyzed. The first group served as a control (no nasal splints), and the second group used the nasal retainer compliantly for at least 6 months postoperatively. All patients had their primary lip repair at 3 months of age. A photographic evaluation of the results when the patients were between 5 and 8 years of age was conducted. The parameters used to assess the nasal outcome were nostril symmetry, alar cartilage slump, alar base level, and columella tilt. The first scores were based on residual nasal deformity, and the second set were based on overall appearance. It was found that the mean scores of residual nasal deformity for all four parameters in patients who used the nasal stent were statistically better than the scores of patients who did not (p values ranged from 0.0001 to 0.005). The overall appearance scores for the four parameters in the patients who used the nasal stent after surgery were also statistically better than the scores for those who did not (p values ranged from 0.0001 to 0.01). The results show that postoperative nasal splinting in the primary management of the unilateral cleft nasal deformity serves to preserve and maintain the corrected position of the nose after primary lip and nasal correction, resulting in a significantly improved aesthetic result. Therefore, it is recommended that all patients undergoing primary correction of complete unilateral cleft deformity use the nasal retainer postoperatively for a period of at least 6 months.

Platelet-rich plasma has no effect on increasing free fat graft survival in the nude mouse.

BACKGROUND Free fat grafts have an unpredictable survival rate, which may be dependent on host bed vascularity. Therefore, the authors hypothesized that the presence of growth factors in platelet-rich plasma (PRP), may enhance free fat graft survival. METHODS Free fat grafts and autologous PRP were harvested from a healthy female and processed using the Coleman technique and the Medtronic Magellan system respectively. The experiment comprised two groups of 12 nude mice each with injection of free fat grafts into the scalp. The experimental group comprised the combination of 0.8 ml of free fat graft and 0.2 ml of PRP. The control group comprised the combination of 0.8 ml of free fat graft and 0.2 ml of normal saline. The mice were euthanized after 16 weeks and the fat grafts explanted and measured for weight and volume. Histology was performed with Oil Red O stain. Statistical analysis of the weight and volume in between groups was performed using the independent samples T-test (SPSS v11). The Mann-Whitney test was used to compare the ranking of six histological parameters between the two groups. RESULTS The mean weight and volume for the experimental arm were 0.503 g and 0.545 ml respectively. The mean weight and volume for the control arm were 0.500 g and 0.541 ml respectively. The weight, volume and histological parameters between the two groups were not statistically significant. A mouse from each group died of unknown causes. CONCLUSION PRP did not enhance free fat graft survival in the nude mouse.

Analysis of candidate genes on chromosome 2 in oral cleft case-parent trios from three populations

Isolated oral clefts, including cleft lip with/without cleft palate (CL/P) and cleft palate (CP), have a complex and heterogeneous etiology. Case-parent trios from three populations were used to study genes spanning chromosome 2, where single nucleotide polymorphic (SNP) markers were analyzed individually and as haplotypes. Case-parent trios from three populations (74 from Maryland, 64 from Singapore and 95 from Taiwan) were genotyped for 962 SNPs in 104 genes on chromosome 2, including two well-recognized candidate genes: TGFA and SATB2. Individual SNPs and haplotypes (in sliding windows of 2–5 SNPs) were used to test for linkage and disequilibrium separately in CL/P and CP trios. A novel candidate gene (ZNF533) showed consistent evidence of linkage and disequilibrium in all three populations for both CL/P and CP. SNPs in key regions of ZNF533 showed considerable variability in estimated genotypic odds ratios and their significance, suggesting allelic heterogeneity. Haplotype frequencies for regions of ZNF533 were estimated and used to partition genetic variance into among-and within-population components. Wright’s fixation index, a measure of genetic diversity, showed little difference between Singapore and Taiwan compared with Maryland. The tensin-1 gene (TNS1) also showed evidence of linkage and disequilibrium among both CL/P and CP trios in all three populations, albeit at a lower level of significance. Additional genes (VAX2, GLI2, ZHFX1B on 2p; WNT6–WNT10A and COL4A3–COL4A4 on 2q) showed consistent evidence of linkage and disequilibrium only among CL/P trios in all three populations, and TGFA showed significant evidence in two of three populations.

Multiple-segment osteotomy in maxillofacial surgery.

Multiple-segment osteotomy is defined as an osteotomy that divides the tooth-bearing arch of the maxilla or mandible into three or more segments. Combining large-segment orthognathic surgery and unitooth or small-segment surgery is an effective approach for dealing with a wide range of dentofacial deformities with occlusal problems. The indications for a multiple-segment osteotomy included dentofacial deformities and malocclusions requiring stable correction within a short overall treatment period. From 1991 to 1997, a total of 85 patients had multiple-segment osteotomy orthognathic procedures performed at Chang Gung Memorial Hospital. The indications for surgery were maxillary protrusion/deformity (31 patients), mandibular prognathism (51 patients), and noncleft maxillary retrusion (three patients). The types of osteotomies performed were Le Fort I, anterior segmental osteotomies of the maxilla or the mandible, palatal split, posterior segment, and unitooth or double-tooth segments. Follow-up ranged from 6 months to 7 years; stability was seen in movements, with only three complications (one partial gingival loss and two inferior mental paresthesias). No osteotomized segments were lost. The average overall treatment time was approximately 15 months, including 3 to 6 months of preoperative and 9 to 12 months of postoperative orthodontic treatment. This is at least 6 months shorter than traditional orthognathic surgery. Experience with 85 consecutive patients has shown that the results are good and the procedure is safe, with minimal complications.

Differential parental transmission of markers in RUNX2 among cleft case-parent trios from four populations

Isolated cleft lip with or without cleft palate (CL/P) is among the most common human birth defects, with a prevalence around 1 in 700 live births. The Runt‐related transcription factor 2 (RUNX2) gene has been suggested as a candidate gene for CL/P based largely on mouse models; however, no human studies have focused on RUNX2 as a risk factor for CL/P. This study examines the association between markers in RUNX2 and isolated, nonsyndromic CL/P using a case‐parent trio design, while considering parent‐of‐origin effects. Case‐parent trios from four populations (77 from Maryland, 146 from Taiwan, 35 from Singapore, and 40 from Korea) were genotyped for 24 single nucleotide polymorphisms (SNPs) in the RUNX2 gene. We performed the transmission disequilibrium test on individual SNPs. Parent‐of‐origin effects were assessed using the transmission asymmetry test and the parent‐of‐origin likelihood ratio test (PO‐LRT). When all trios were combined, the transmission asymmetry test revealed a block of 11 SNPs showing excess maternal transmission significant at the P<0.01 level, plus one SNP (rs1934328) showing excess paternal transmission (P=0.002). For the 11 SNPs showing excess maternal transmission, odds ratios of being transmitted to the case from the mother ranged between 3.00 and 4.00. The parent‐of‐origin likelihood ratio tests for equality of maternal and paternal transmission were significant for three individual SNPs (rs910586, rs2819861, and rs1934328). Thus, RUNX2 appears to influence risk of CL/P through a parent‐of‐origin effect with excess maternal transmission. Genet. Epidemiol. 2008.

The FGF and FGFR Gene Family and Risk of Cleft Lip With or Without Cleft Palate

Background Isolated, nonsyndromic cleft lip with or without cleft palate is a common human congenital malformation with a complex and heterogeneous etiology. Genes coding for fibroblast growth factors and their receptors (FGF/FGFR genes) are excellent candidate genes. Methods We tested single-nucleotide polymorphic markers in 10 FGF/FGFR genes (including FGFBP1, FGF2, FGF10, FGF18, FGFR1, FGFR2, FGF19, FGF4, FGF3, and FGF9) for genotypic effects, interactions with one another, and with common maternal environmental exposures in 221 Asian and 76 Maryland case-parent trios ascertained through a child with isolated, nonsyndromic cleft lip with or without cleft palate. Results Both FGFR1 and FGF19 yielded evidence of linkage and association in the transmission disequilibrium test, confirming previous evidence. Haplotypes of three single-nucleotide polymorphisms in FGFR1 were nominally significant among Asian trios. Estimated odds ratios for individual single-nucleotide polymorphic markers and haplotypes of multiple markers in FGF19 ranged from 1.31 to 1.87. We also found suggestive evidence of maternal genotypic effects for markers in FGF2 and FGF10 among Asian trios. Tests for gene-environment (G x E) interaction between markers in FGFR2 and maternal smoking or multivitamin supplementation yielded significant evidence of G x E interaction separately. Tests of gene-gene (G x G) interaction using Cordells method yielded significant evidence between single-nucleotide polymorphisms in FGF9 and FGF18, which was confirmed in an independent sample of trios from an international consortium. Conclusion Our results suggest several genes in the FGF/FGFR family may influence risk for isolated, nonsyndromic cleft lip with or without cleft palate through distinct biological mechanisms.

Maternal transmission effects of the PAX genes among cleft case–parent trios from four populations

Isolated cleft lip with or without cleft palate (CL/P) is among the most common human birth defects, with a prevalence of 1 in 700 live births. The paired box (PAX) genes have been suggested as candidate genes for CL/P based largely on mouse models; however, few human studies have focused on this gene family. This study tests for association between markers in four PAX genes and CL/P using a case-parent trio design considering parent-of-origin effects. Trios from four populations (76 from Maryland, 146 from Taiwan, 35 from Singapore, and 40 from Korea) were genotyped for 34 single nucleotide polymorphisms (SNPs) in the PAX3, PAX6, PAX7, and PAX9 genes. We performed the transmission disequilibrium test (TDT) on individual SNPs. Parent-of-origin effects were assessed using the transmission asymmetry test (TAT) and the parent-of-origin likelihood ratio test (PO-LRT). TDT analysis showed one SNP (rs766325) in PAX7 yielding evidence of linkage and association when parent-of-origin was not considered, with an OR(transmission)=1.62 (P=0.003), and five SNPs in PAX6 (including two pairs in near perfect linkage disequilibrium). TAT analysis of all trios revealed two SNPs in PAX7 and four SNPs in PAX3 showing significant excess maternal transmission. For these six SNPs, the maternal OR(transmission) ranged between 1.74 and 2.40, and PO-LRT was also significant (P-values=0.035–0.012). When this analysis was limited to trios with male cases, SNPs in PAX7 showed higher maternal OR(transmission) and greater significance. PAX genes may influence the risk of CL/P through maternal effects, possibly imprinting, which seems to be stronger among male cases.