Data from: RUNX2 tandem repeats and the evolution of facial length in placental mammals

BACKGROUND: When simple sequence repeats are integrated into functional genes, they can potentially act as evolutionary 'tuning knobs', supplying abundant genetic variation with minimal risk of pleiotropic deleterious effects. The genetic basis of variation in facial shape and length represents a possible example of this phenomenon. Runt-related transcription factor 2 (RUNX2) which is involved in osteoblast differentiation, contains a functionally-important tandem repeat of glutamine and alanine amino acids. The ratio of glutamines to alanines (the QA ratio) in this protein seemingly influences the regulation of bone development. Notably, in domestic breeds of dog, and in carnivorans in general, the ratio of glutamines to alanines is strongly correlated with facial length. RESULTS: In this study we examine whether this correlation holds true across placental mammals, particularly those mammals for which facial length is highly variable and related to adaptive behavior and lifestyle (e.g., primates, afrotherians, xenarthrans). We obtained relative facial length measurements and RUNX2 sequences for 41 mammalian species representing 12 orders. Using both a phylogenetic generalized least squares model and recently-developed Bayesian comparative method, we tested for a correlation between genetic and morphometric data while controlling for phylogeny, evolutionary rates, and divergence times. Non-carnivoran taxa generally had substantially lower glutamine-alanine ratios than carnivorans (primates and xenarthrans with means of 1.34 and 1.25, respectively, compared to a mean of 3.1 for carnivorans), and we found no correlation between RUNX2 sequence and face length across placental mammals. CONCLUSIONS: Results of our diverse comparative phylogenetic analyses indicate that QA ratio does not consistently correlate with face length across the 41 mammalian taxa considered. Thus, although RUNX2 might function as a 'tuning knob' modifying face length in carnivorans, this relationship is not conserved across mammals in general.背景：当简单序列重复整合入功能基因后，它们可作为进化层面的“调节旋钮”，可产生丰富的遗传变异，且仅伴随极低的多效性有害效应风险。面部形态与长度变异的遗传基础，便是这一现象的潜在例证。参与成骨细胞分化的Runt相关转录因子2（RUNX2）包含一段具有重要功能的谷氨酰胺与丙氨酸氨基酸串联重复序列。该蛋白中谷氨酰胺与丙氨酸的比值（QA比值）似乎会影响骨骼发育的调控。值得注意的是，在家犬品种乃至整体食肉目动物中，谷氨酰胺与丙氨酸的比值与面部长度存在强相关性。 结果：本研究旨在探究该相关性是否在胎盘类哺乳动物中成立，尤其是那些面部长度高度可变且与适应性行为及生活方式相关的类群（如灵长类、非洲兽类、异关节类）。我们为涵盖12个目、共41个哺乳动物物种获取了相对面部长度测量值与RUNX2序列。通过系统发育广义最小二乘模型以及新近开发的贝叶斯比较方法，我们在控制系统发育、进化速率与分化时间的前提下，检验了遗传数据与形态测量数据之间的相关性。非食肉目类群的谷氨酰胺-丙氨酸比值普遍显著低于食肉目类群（灵长类与异关节类的平均值分别为1.34和1.25，而食肉目类群的平均值为3.1），且我们未在全体胎盘类哺乳动物中发现RUNX2序列与面部长度存在相关性。 结论：多样的比较系统发育分析结果表明，在所纳入的41个哺乳类类群中，QA比值与面部长度并不存在普遍的相关性。因此，尽管RUNX2或许可作为食肉目动物中调控面部长度的“调节旋钮”，但这一关联并非在全体哺乳动物中都保守存在。