Genetic selection of athletic success in sport-hunting dogs.

Modern dogs are distinguished among domesticated species by the vast breadth of phenotypic variation produced by strong and consistent human-driven selective pressure. The resulting breeds reflect the development of closed populations with well-defined physical and behavioral attributes. The sport-hunting dog group has long been employed in assistance to hunters, reflecting strong behavioral pressures to locate and pursue quarry over great distances and variable terrain. Comparison of whole-genome sequence data between sport-hunting and terrier breeds, groups at the ends of a continuum in both form and function, reveals that genes underlying cardiovascular, muscular, and neuronal functions are under strong selection in sport-hunting breeds, including ADRB1, TRPM3, RYR3, UTRN, ASIC3, and ROBO1 We also identified an allele of TRPM3 that was significantly associated with increased racing speed in Whippets, accounting for 11.6% of the total variance in racing performance. Finally, we observed a significant association of ROBO1 with breed-specific accomplishments in competitive obstacle course events. These results provide strong evidence that sport-hunting breeds have been adapted to their occupations by improved endurance, cardiac function, blood flow, and cognitive performance, demonstrating how strong behavioral selection alters physiology to create breeds with distinct capabilities.

Analysis of large versus small dogs reveals three genes on the canine X chromosome associated with body weight, muscling and back fat thickness.

Domestic dog breeds display significant diversity in both body mass and skeletal size, resulting from intensive selective pressure during the formation and maintenance of modern breeds. While previous studies focused on the identification of alleles that contribute to small skeletal size, little is known about the underlying genetics controlling large size. We first performed a genome-wide association study (GWAS) using the Illumina Canine HD 170,000 single nucleotide polymorphism (SNP) array which compared 165 large-breed dogs from 19 breeds (defined as having a Standard Breed Weight (SBW) >41 kg [90 lb]) to 690 dogs from 69 small breeds (SBW ≤41 kg). We identified two loci on the canine X chromosome that were strongly associated with large body size at 82-84 megabases (Mb) and 101-104 Mb. Analyses of whole genome sequencing (WGS) data from 163 dogs revealed two indels in the Insulin Receptor Substrate 4 (IRS4) gene at 82.2 Mb and two additional mutations, one SNP and one deletion of a single codon, in Immunoglobulin Superfamily member 1 gene (IGSF1) at 102.3 Mb. IRS4 and IGSF1 are members of the GH/IGF1 and thyroid pathways whose roles include determination of body size. We also found one highly associated SNP in the 5'UTR of Acyl-CoA Synthetase Long-chain family member 4 (ACSL4) at 82.9 Mb, a gene which controls the traits of muscling and back fat thickness. We show by analysis of sequencing data from 26 wolves and 959 dogs representing 102 domestic dog breeds that skeletal size and body mass in large dog breeds are strongly associated with variants within IRS4, ACSL4 and IGSF1.

Aberrant overexpression of the Rgl2 Ral small GTPase-specific guanine nucleotide exchange factor promotes pancreatic cancer growth through Ral-dependent and Ral-independent mechanisms.

Our recent studies established essential and distinct roles for RalA and RalB small GTPase activation in K-Ras mutant pancreatic ductal adenocarcinoma (PDAC) cell line tumorigencity, invasion, and metastasis. However, the mechanism of Ral GTPase activation in PDAC has not been determined. There are four highly related mammalian RalGEFs (RalGDS, Rgl1, Rgl2, and Rgl3) that can serve as Ras effectors. Whether or not they share distinct or overlapping functions in K-Ras-mediated growth transformation has not been explored. We found that plasma membrane targeting to mimic persistent Ras activation enhanced the growth-transforming activities of RalGEFs. Unexpectedly, transforming activity did not correlate directly with total cell steady-state levels of Ral activation. Next, we observed elevated Rgl2 expression in PDAC tumor tissue and cell lines. Expression of dominant negative Ral, which blocks RalGEF function, as well as interfering RNA suppression of Rgl2, reduced PDAC cell line steady-state Ral activity, growth in soft agar, and Matrigel invasion. Surprisingly, the effect of Rgl2 on anchorage-independent growth could not be rescued by constitutively activated RalA, suggesting a novel Ral-independent function for Rgl2 in transformation. Finally, we determined that Rgl2 and RalB both localized to the leading edge, and this localization of RalB was dependent on endogenous Rgl2 expression. In summary, our observations support nonredundant roles for RalGEFs in Ras-mediated oncogenesis and a key role for Rgl2 in Ral activation and Ral-independent PDAC growth.

Genetic and pharmacologic dissection of Ras effector utilization in oncogenesis.

Ras proteins function as signaling nodes that are activated by diverse extracellular stimuli. Equally complex for this family of molecular switches is the multitude of downstream effectors and the pathways that they traverse to translate extracellular signals into a spectrum of cellular consequences. To better understand the individual and collective roles of these effector signaling networks, both genetic and pharmacological tools have been developed. By either stimulating or ablating specific components in a cascade downstream of Ras activation, one can gain insight into the specific signaling underlying a particular Ras phenotype, for example, malignant transformation. In this chapter, we describe the use of activating and dominant-negative mutations, both artificial and naturally occurring, of Ras and its effectors, as well as pharmacological inhibitors used to probe the effector pathways (Raf kinase, phosphoinositol 3-kinase, Tiam1, phospholipase C epsilon, and RalGEF) implicated in Ras-mediated oncogenesis.