Following recent genome wide association studies (GWAS), significant genetic associations have been identified for several genes with non-syndromic cleft lip with or without cleft palate (CL(P). To replicate two of these GWAS signals, we investigated the role of common and rare variants in the PAX7 and VAX1 genes. TaqMan genotyping was carried out for SNPs in VAX1 and PAX7 and Transmission Disequilibrium Test (TDT) was performed to test for linkage and association in each population. Direct sequencing in and around the PAX7 and VAX1 genes in 1,326 individuals of European and Asian ancestry was done. TDT analysis showed strong associations with markers in VAX1 (rs7078160, p=2.7E-06 and rs475202, p=0.0002) in a combined sample of Mongolian and Japanese CL (P) case-parent triads. Analyses using parent-of-origin effects showed significant excess transmission of the minor allele from both parents with the effect in the mothers (p=6.5E-05, OR (transmission) =1.91) more striking than in the fathers (p=0.004, OR (transmission) =1.67) for VAX1 marker rs7078160 in the combined Mongolian and Japanese samples when all cleft types were combined. The rs6659735 trinucleotide marker in PAX7 was significantly associated with all the US cleft groups combined (p=0.007 in all clefts and p=0.02 in CL(P)). Eight rare missense mutations found in PAX7 and two rare missense mutations in VAX1. Our study replicated previous GWAS findings for markers in VAX1 in the Asian population, and identified rare variants in PAX7 and VAX1 that may contribute to the etiology of CL(P). Determining the role of rare variants clearly warrants further investigation.

No abstract

It is well-known that TCDD (2,3,7,8, tetrachloridedibenzo-p-dioxin) induces cleft palates (CPs) in pregnant C57BL mice. However, it is unclear if TCDD is a possible teratogen for cleft lip. We examined maxillofacial malformations including cleft lip in three animal strains: A/J mice, C57BL/6J mice and ICR mice. The A/J mouse develops cleft lip and palate spontaneously at a 5-10% rate. TCDD was administered in olive oil on gestation day (GD) 12.5 with gastric tubes at 10 microg/kg, 20 microg/kg, or 40 microg/kg to examine the dose-response, and on a single day from GD 8.5-14.5 to examine the timing effects of TCDD administration on lip and palate formation. Furthermore, the palatal shelf movements during GD 8.5-14.5 were observed with a stereoscopic microscope. All embryos had cleft palates when the TCDD was administered just before palatogenesis (GD11.5-GD12.5). With respect to the TCDD effects, there were large differences among the strains. In the A/J mice, the difference between a lethal dose and a dose that could induce a cleft palate was close. Cleft lips were not induced, even when the TCDD was given just before labiogenesis. Morphologically, both palatal shelves contacted perfectly along their lengths, but separated and formed cleft palates. In conclusion, TCDD is a strong inducer of cleft palates, and interferes with the fusion phase of the secondary palate, but has no effect on the lip.

The effect of thyrotropin-releasing hormone (TRH) on the mechanism regulating growth hormone (GH) secretion was investigated in urethane-anesthetized male rats. The iv injection of TRH (0.2 and 3 mug/100 g BW) caused a significant and dose-related increase in plasma GH. Greater GH responses to TRH were not obtained with doses of TRH larger than 5 mug/100 g BW. TRH injection also raised plasma GH in rats subjected to hypothalamic ablation, in which the maximum increments of plasma GH after TRH injection were greater than in control rats. Plasma GH responses to the iv injection of chlorpromazine (200 mug/100 g BW) were significantly augmented by the concomitant iv injection of TRH in a dose of 3 mug/100 g BW. However, a large dose of TRH (25 mug/100 g BW) injected with chlorpromazine caused a significantly smaller increase in plasma GH than did smaller doses of TRH (0.2 and 3 mug/100 g BW). TRH injection into the lateral ventricle (0.02 and 0.2 mug/100 g BW) inhibited significantly the GH release induced by chlorpromazine, whereas TRH (0.2 mug/100 g BW) alone caused only a slight increase in plasma GH. These results suggest that TRH may not only stimulate GH release by a direct action on the pituitary, but may also modify GH secretion by acting through the central nervous system.

Morphological and immunohistological examinations were performed to reveal the mechanisms of cleft palate induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). ICR strain mice 8-10 weeks of age were used in the study. TCDD was administered in olive oil on gestation day (GD) 12.5 with gastric tubes at 40 microg/kg. From GD 13.5 to 16.5, palates were examined by scanning electron microscopy (SEM), hematoxyline-eosin (HE) staining, and immunohistochemical staining of FGFR1/2, TGF-beta3, MSX1 and LHX8. In the control group, both of the palatal shelves began elevating on GD 14.0 and finished within 6 h. After the elevation, all of the shelves had completely fused with each other on GD 14.5. In the TCDD-treated group, palatal shelves elevated 1 day later than in the control group. However, all palates had elevated by GD 15.0. After the elevation, the shelves contacted each other and fused; however, they were separated on GD16.0. HE staining showed that medial edge epithelium (MEE) was thinner in the TCDD group than in the control group. MEE observed under a high magnification (x2500) exhibited filopodia-like filaments and the cells were bulged in the control group. In contrast, in the TCDD group, no filaments were observed and the cells were flat with unclear boundaries. Immunohistologically, there were no characteristic findings except for FGFR1. FGFR1 was not expressed in the TCDD group after the fusion phase (GD 14.5). TCDD induces many morphological and molecular changes to MEE cells and causes cleft palates.

No abstract

SPECC1L mutations have been identified in patients with rare atypical orofacial clefts and with syndromic cleft lip and/or palate (CL/P). These mutations cluster in the second coiled-coil and calponin homology domains of SPECC1L and severely affect the ability of SPECC1L to associate with microtubules. We previously showed that gene-trap knockout of Specc1l in mouse results in early embryonic lethality. We now present a truncation mutant mouse allele, Specc1lΔC510, that results in perinatal lethality. Specc1lΔC510/ΔC510 homozygotes showed abnormal palate rugae but did not show cleft palate. However, when crossed with a gene-trap allele, Specc1lcGT/ΔC510 compound heterozygotes showed a palate elevation delay with incompletely penetrant cleft palate. Specc1lcGT/ΔC510 embryos exhibit transient oral epithelial adhesions at E13.5, which may delay shelf elevation. Consistent with oral adhesions, we show periderm layer abnormalities, including ectopic apical expression of adherens junction markers, similar to Irf6 hypomorphic mutants and Arhgap29 heterozygotes. Indeed, SPECC1L expression is drastically reduced in Irf6 mutant palatal shelves. Finally, we wanted to determine if SPECC1L deficiency also contributed to non-syndromic (ns) CL/P. We sequenced 62 Caucasian, 89 Filipino, 90 Ethiopian, 90 Nigerian and 95 Japanese patients with nsCL/P and identified three rare coding variants (p.Ala86Thr, p.Met91Iso and p.Arg546Gln) in six individuals. These variants reside outside of SPECC1L coiled-coil domains and result in milder functional defects than variants associated with syndromic clefting. Together, our data indicate that palate elevation is sensitive to deficiency of SPECC1L dosage and function and that SPECC1L cytoskeletal protein functions downstream of IRF6 in palatogenesis.

No abstract