Complex genetic architecture of three-dimensional craniofacial shape variation in domestic pigeons

Complex and Dynamic Gene-by-Age and Gene-by-Environment Interactions Underlie Functional Morphological Variation in Adaptive Divergence in Arctic Charr (Salvelinus alpinus)

The evolution of adaptive phenotypic divergence requires heritable genetic variation. However, it is underappreciated that trait heritability is molded by developmental processes interacting with the environment. We hypothesized that the genetic architecture of divergent functional traits was dependent on age and foraging environment. Thus, we induced plasticity in full-sib families of Arctic charr (Salvelinus alpinus) morphs from two Icelandic lakes by mimicking prey variation in the wild. We characterized variation in body shape and size at two ages and investigated their genetic architecture with quantitative trait locus (QTL) analysis. Age had a greater effect on body shape than diet in most families, suggesting that development strongly influences phenotypic variation available for selection. Consistent with our hypothesis, multiple QTL were detected for all traits and their location depended on age and diet. Many of the genome-wide QTL were located within a subset of duplicated chromosomal regions suggesting that ancestral whole genome duplication events have played a role in the genetic control of functional morphological variation in the species. Moreover, the detection of two body shape QTL after controlling for the effects of age provides additional evidence for genetic variation in the plastic response of morphological traits to environmental variation. Thus, functional morphological traits involved in phenotypic divergence are molded by complex genetic interactions with development and environment.

Cellular, Molecular, and Genetic Mechanisms of Avian Beak Development and Evolution

Diverse research programs employing complementary strategies have been uncovering cellular, molecular, and genetic mechanisms essential to avian beak development and evolution. In reviewing these discoveries, I offer an interdisciplinary perspective on bird beaks that spans their derivation from jaws of dinosaurian reptiles, their anatomical and ecological diversification across major taxonomic groups, their common embryonic origins, their intrinsic patterning processes, and their structural integration. I describe how descriptive and experimental approaches, including gene expression and cell lineage analyses, tissue recombinations, surgical transplants, gain- and loss-of-function methods, geometric morphometrics, comparative genomics, and genome-wide association studies, have identified key constituent parts and putative genes regulating beak morphogenesis and evolution. I focus throughout on neural crest mesenchyme, which generates the beak skeleton and other components, and describe how these embryonic progenitor cells mediate species-specific pattern and link form and function as revealed by 20 years of research using chimeras between quail and duck embryos.

Genome-wide association study of growth traits and validation of key mutations (MSTN c.C861T) associated with the muscle mass of meat pigeons

Selective breeding of meat pigeons is primarily based on growth traits, especially muscle mass (MM). Identification of functional genes and molecular markers of growth and slaughter traits through a genome-wide association study (GWAS) will help to elucidate the underlying molecular mechanisms and provide a theoretical basis for the selective breeding of meat pigeons. The phenotypic data of body weight (BW) and body size (BS) of 556 meat pigeons at 52 and 80 weeks of age were collected. In total, 160 434 high-quality single nucleotide polymorphism sites were obtained by restriction site-associated DNA sequencing. The GWAS analysis revealed that MSTN, IGF2BP3 and NCAPG/LCORL were important candidate genes affecting the growth traits of meat pigeons. IGF2BP3 and NCAPG/LCORL were highly correlated to BW and BS, which are related to overall growth and development, while MSTN was associated with pectoral thickness and BW. Phenotypic association validation with the use of two meat pigeon populations found that the MSTN mutation c.C861T determines the MM. These results provide new insights into the genetic mechanisms underlying phenotypic variations of growth traits and MM in commercial meat pigeons. The identified markers and genes provide a theoretical basis for the selective breeding of meat pigeons.

Chicken HOXC8 and HOXC10 genes may play a role in the altered skull morphology associated with the Crest phenotype

One of the most intriguing traits found in domestic chickens is the Crest phenotype. This trait, characterized by a tuft of elongated feathers sprouted from the head, is found in breeds such as Polish chickens and Silkie chickens. Moreover, some crested chicken breeds also exhibit a protuberance in their anterodorsal skull region. Previous studies have strived to identify the causative factors of this trait. This study aimed to elucidate the role of chicken HOXC8 and HOXC10 in the formation of the Crest phenotype. We explored the effect of ectopic expression of HOXC8 or HOXC10 on the chicken craniofacial morphology using the RCAS retrovirus transformation system. Microcomputed tomography scanning was conducted to measure the 3D structure of the cranial bone of transgenic embryos for geometric morphometric analysis. We found that the ectopic expression of HOXC8 or HOXC10 in chicken heads caused mild morphological changes in the skull compared with the GFP-transgenic control group. Geometric morphometric analysis showed that HOXC8 and HOXC10 transgenic groups expressed a mild upward shape change in the frontal region of the skull compared with the control group, which is similar to what is seen in the crested chicken breeds. In conclusion, this study supports findings in previous studies in which HOX genes play a role in the formation of the altered skull morphology related to the Crest phenotype. It also supports that mutations in HOX genes may contribute to intra- and inter-specific variation in morphological traits in vertebrates.