Is craniofacial morphology and body composition related by common genes: Comparative analysis of two ethnically diverse populations

OBJECTIVES

The overarching hypothesis of the present paper is that ethnically and/or genetically diverse human populations may exhibit similarity in correlations between various aspects of human phenotypes due to the morphological integration process during the ontogenetic stages. To test this we investigated whether an association between craniofacial (CF) features and body composition (BC) variations is present in humans and the extent to which such possible associations are comparable in different populations. Furthermore, the paper examines the contribution of common genetic (additive) and shared familial environmental factors in assessing the correlation between CF and BC characteristics in humans.

MATERIALS AND METHODS

Two pedigree-based samples were collected from two distinct populations, including India (Santhal) and Europe (Chuvash). Canonical correlation analysis was used to compare the association between CF and BC characteristics in the two studied samples. The contribution of genetic and familial environmental factors on the correlation between CF and BC features was analyzed through variance decomposition analysis by implementing the Mendelian Analysis package (MAN).

RESULTS

Our study suggests that CF morphology is significantly (p < 0.001) associated with BC variation in both samples. CF characteristics and BC phenotypes revealed a consistent trend in both samples where condensed and broad CF morphology was significantly associated with increased fat accumulation, with slight variations between the Santhal and Chuvash samples. Despite the variations observed between the samples, the heritability estimates were impressively equivalent for traits like total facial height (55.6%_Santhal vs.56.1%_Chuvash ) and nasal index (42.8%_Santhal vs. 43.3%_Chuvash ).

DISCUSSION

The genetic contribution of CF morphology appeared to be extensive and the contribution of common genetic and shared family environmental correlations between CF and BC measures were suggestively substantial. Accordingly, these correlations were consistently observed across ethnically diverse populations, despite drastic morphological differences between the samples under comparison.

Photoanthropometric study of craniofacial traits in individuals with Williams syndrome

A photoanthropometric method, which enables an objective description of facial structures, was used to better delineate the craniofacial characteristics of 29 individuals with Williams syndrome (WS; 18 males and 11 females) between the ages of 0 to 10 years, with an average age of 4.0 years. Facial parameters were measured from strict frontal and profile photographic 35-mm slides and compared with other facial measurements from the same face (e.g., palpebral fissure width to bizygomatic diameter). Sixteen photoanthropometric craniofacial indices were developed from 20 measurements (3 from the frontal face, 2 from the eye region, 3 from the nose region, 2 from the mouth region, 4 from the profile face, and 6 from the ear region). Based on our measurements of 29 Williams syndrome individuals, two parameters (e.g. nose length to midface height and palpebral fissure width to bizygomatic diameter) were outside the normal range when compared with photoanthropometric index standards for age established by Stengel-Rutkowski et al. from white control children. Overall, our data supported a high midface height, broad palpebral fissure width, broad interalar distance, short length of back of nose, prominent ears with long narrow conchae, increased chin height, increased inclination of the ears and a narrow bizygomatic diameter in WS patients. These craniofacial parameters (many not previously evaluated in WS patients) may become useful for early detection, and aid in the diagnosis and study of the development of the characteristic face in Williams syndrome subjects.