Morphometric analysis of heterozygote dancer mice predisposed to 6-aminonicotinamide-induced cleft lip

What’s Shape Got to Do With It? Examining the Relationship Between Facial Shape and Orofacial Clefting

Nonsyndromic orofacial clefts belong to a class of congenital malformations characterized by a complex and multifactorial etiology. During early facial development, multiple factors can disrupt fusion leading to a cleft; this includes the shape of the embryonic face. The face shape hypothesis (FSH) of orofacial clefting emerged in the 1960s, influenced by morphological differences observed within affected families, comparative studies of mouse models, and advances in modeling genetic liability for complex traits in populations. For the past five decades, studies have documented changes in the shape or spatial arrangement of facial prominences in embryonic mice and altered post-natal facial shape in individuals at elevated risk for orofacial clefting due to their family history. Moreover, recent studies showing how genes that impact facial shape in humans and mice are providing clues about the genetic basis of orofacial clefting. In this review, I discuss the origins of the FSH, provide an overview of the supporting evidence, and discuss ways in which the FSH can inform our understanding of orofacial clefting.

Three-dimensional morphometric analysis of craniofacial shape in the unaffected relatives of individuals with nonsyndromic orofacial clefts: a possible marker for genetic susceptibility

Numerous studies have described altered patterns of craniofacial form in the unaffected relatives of individuals with nonsyndromic clefts. Unfortunately, results from such studies have been highly variable and have failed to provide a reliable method for differentiating "at-risk" relatives from controls. In the present study, we compared craniofacial shape between a sample of unaffected relatives (33 females; 14 males) from cleft multiplex families and an equal number of age/sex/ethnicity-matched controls. Sixteen x,y,z facial landmark coordinates derived from 3D photogrammetry were analyzed via Euclidean Distance Matrix Analysis, while 14 additional linear distances were analyzed via t tests. A subset of variables was then entered into a discriminant function analysis (DFA). Compared to controls, female unaffected relatives demonstrated increased upper facial width, midface reduction and lateral displacement of the alar cartilage. DFA correctly classified 70% of female unaffected relatives and 73% of female controls. Male unaffected relatives demonstrated increased upper facial and cranial base width, increased lower facial height and decreased upper facial height compared with controls. DFA correctly classified 86% of male unaffected relatives and 93% of male controls. In both sexes, upper facial width contributed most to group discrimination. Following DFA, unaffected relatives were assigned to risk/liability classes based on the degree of phenotypic divergence from controls. Results indicate that craniofacial shape differences characterizing unaffected relatives are partly sex-specific and are in broad agreement with previous reports. These findings further suggest that a quantitative assessment of the craniofacial phenotype may allow for the identification of susceptible individuals within nonsyndromic cleft families.

Effect of the dam strain on the spontaneous incidence of cleft lip and palate and intrauterine growth of CL/Fr mouse fetuses

PURPOSE

The effects of dam strain on the spontaneous incidence of the cleft lip and palate (CLP) and the intrauterine growth of transferred CLP-susceptible CL/Fr embryos were examined with an embryo transfer technique. The CL/Fr strain of embryos at the early blastocyst stage was transferred to the same dam strain and also to the CLP-resistant C57BL dam strain. A laparotomy was done on the 18th gestational day at which time the number of fetuses, the resorption sites and the fetus weight were recorded. Each fetus was checked for the presence of CLP. Five criteria to assess the reproduction and fertility as well as the fetus weight were then compared between both dam strains.

RESULTS

The dam pregnancy rate and the fetus survival rate in the CL/Fr dam strain were both significantly lower than those in the C57BL dam strain. The resorption rate in the CL/Fr dam strain was significantly higher than that in the C57BL dam strain. The spontaneous incidence rate of CLP in the CL/Fr dam strain was also significantly higher than that in the C57BL dam strain. The fetus weight of the CL/Fr fetuses developed in the CL/Fr dam strain was significantly lighter than that of the CL/Fr fetuses developed in the C57BL dam strain.

CONCLUSION

The results indicated that the CLP-susceptible CL/Fr dam strain provided a less favorable uterine environment for the implantation, survival and intrauterine growth of the transferred CL/Fr embryos and also caused a higher spontaneous incidence rate of CLP. Thus, it can be concluded that the effect of the dam strain appears to play an important role on the spontaneous incidence of CLP and the intrauterine growth of the CL/Fr strain embryos transferred to both CL/Fr and C57BL dam strains.