The Tabby cat locus maps to feline chromosome B1

Developmental genetics of color pattern establishment in cats

Intricate color patterns are a defining aspect of morphological diversity in the Felidae. We applied morphological and single-cell gene expression analysis to fetal skin of domestic cats to identify when, where, and how, during fetal development, felid color patterns are established. Early in development, we identify stripe-like alterations in epidermal thickness preceded by a gene expression pre-pattern. The secreted Wnt inhibitor encoded by Dickkopf 4 plays a central role in this process, and is mutated in cats with the Ticked pattern type. Our results bring molecular understanding to how the leopard got its spots, suggest that similar mechanisms underlie periodic color pattern and periodic hair follicle spacing, and identify targets for diverse pattern variation in other mammals.

Mining the 99 Lives Cat Genome Sequencing Consortium database implicates genes and variants for the Ticked locus in domestic cats (Felis catus)

Tabby patterns of fur coats are defining characteristics in wild and domestic felids. Historically, three autosomal alleles at one locus (Tabby): Abyssinian (Ta ; a.k.a. ticked), mackerel (Tm ; a.k.a. striped) and blotched (tb ; a.k.a. classic, blotched) were thought to control these patterns in domestic cats and their breeds. Currently, at least three loci influence cat tabby markings, two of which are designated Tabby and Ticked. The Tabby locus is laeverin (LVRN) and affects the mackerel and blotched patterns. The unidentified gene for the Ticked locus on cat chromosome B1 was suggested to control the presence or absence of the ticked pattern (Tabby - Abyssinian (Ta ; a.k.a. ticked). The cat reference genome (Cinnamon, the Abyssinian) has the ticked phenotype and the variant dataset and coat phenotypes from the 99 Lives Cat Genome Consortium (195 cats) were used to identify candidate genes and variants associated with the Ticked locus. Two strategies were used to find the Ticked allele(s), one considered Cinnamon with the reference allele or heterozygous (Strategy A) and the other considered Cinnamon as having the variant allele or heterozygous (Strategy B). For Strategy A, two variants in Dickkopf Wnt Signaling Pathway Inhibitor 4 (DKK4), a p.Cys63Tyr (B1:41621481, c.188G>A) and a less common p.Ala18Val (B1:42620835, c.53C>T) variant are suggested as two alleles influencing the Ticked phenotype. Bioinformatic and molecular modeling analysis suggests that these changes disrupt a key disulfide bond in the Dkk4 cysteine-rich domain 1 or Dkk4 signal peptide cleavage respectively. All coding variants were excluded as Ticked alleles using Strategy B.

Siberian cats help in solving part of the mystery surrounding golden cats

Golden cats have been appreciated since the beginning of the cat fancy. Golden is a modification of the tabby coat. In the Siberian breed, a specific golden phenotype, named sunshine, has been described. Sunshine tabby cats exhibit a warm tone of tabby, a pink nose lacking the black lining and a large light cream area around the nose. Pedigree analyses revealed an autosomal recessive inheritance pattern. A single candidate region was identified by genome-wide association study (GWAS) and homozygosity mapping. Within that region, we identified CORIN (Corin, serine peptidase) as a strong candidate gene, since CORIN variants have been identified in mice and tigers with a golden phenotype and CORIN has been described as a modifier of the ASIP (Agouti Signaling Protein) pathway. A homozygous CORIN:c.2383C>T missense variant was identified in sunshine tabby cats. Segregation of the variant was consistent with recessive inheritance. The variant was also found in three Kurilian bobtail cats and in two ToyBob cats from the 99 Lives dataset but genotyping of 106 cats from 13 breeds failed to identify carriers in cats from other breeds. The CORIN:c.2383C>T variant was predicted to change an arginine to a cysteine at position 795 in the protein: CORIN:p.(Arg795Cys). Finally, hair observation in Siberian cats was consistent with elongated ASIP signaling as golden hair showed a large yellow band instead of the short subapical one usually observed in agouti hair. These results support an association of the Siberian sunshine modification with the CORIN:c.2383C>T variant. The Siberian cat has helped us to decipher one of the golden phenotypes observed in cats and we propose that the CORIN:c.2383C>T variant represents the wb^SIB (Siberian recessive wideband) allele in the domestic cat.

Periodic patterns in Rodentia: Development and evolution

Mammalian periodic pigment patterns, such as spots and stripes, have long interested mathematicians and biologists because they arise from non-random developmental processes that are programmed to be spatially constrained, and can therefore be used as a model to understand how organized morphological structures develop. Despite such interest, the developmental and molecular processes underlying their formation remain poorly understood. Here, we argue that Arvicanthines, a clade of African rodents that naturally evolved a remarkable array of coat patterns, represent a tractable model system in which to dissect the mechanistic basis of pigment pattern formation. Indeed, we review recent insights into the process of stripe formation that were obtained using an Arvicanthine species, the African striped mouse (Rhabdomys pumilio), and discuss how these rodents can be used to probe deeply into our understanding of the factors that specify and implement positional information in the skin. By combining naturally evolved pigment pattern variation in rodents with classic and novel experimental approaches, we can substantially advance our understanding of the processes by which spatial patterns of cell differentiation are established during embryogenesis, a fundamental question in developmental biology.

Investigation of inherited diseases in cats

Practical relevance:

The health of the cat mirrors a complex interaction between its environment (nurture) and its genetics (nature). To date, over 70 genetic mutations (variants) have been defined in the cat; many involve diseases, structural anomalies, coat color and texture, including numerous that are clinically relevant. This trend will continue as more of the feline genome is deciphered. Genetic testing, and eventually whole-genome sequencing, should become routine diagnostic tools in feline healthcare within the foreseeable future.

Global importance:

Cat breeds have dispersed around the world. Thus, feline medicine clinicians should be aware of breeds common to their region and common mutations found within those regional populations. Random-bred populations of domestic cats can also have defined genetic characteristics and mutations, which are equally worthy of understanding by feline medicine clinicians.

Outline:

This article reviews the chronology and evolution of genetic and genomic tools pertinent to feline medicine. Possible strategies for mapping genetic traits and defects, and how these impact on feline health, are also discussed. The focus is on three historical periods: (1) research conducted before the availability of the cat genome; (2) research performed immediately after the availability of sequences of the cat genome; and (3) current research that goes beyond one cat genome and utilizes the genome sequences of many cats.

Evidence base:

The data presented are extracted from peer-reviewed publications pertaining to mutation identification, and relevant articles concerning heritable traits and/or diseases. The authors draw upon their personal experience and expertise in feline genetics.

DNA mutations of the cat: the good, the bad and the ugly

PRACTICAL RELEVANCE

The health of the cat is a complex interaction between its environment (nurture) and its genetics (nature). Over 70 genetic mutations (variants) have been defined in the cat, many involving diseases, structural abnormalities and clinically relevant health concerns. As more of the cat's genome is deciphered, less commonly will the term 'idiopathic' be used regarding the diagnosis of diseases and unique health conditions. State-of-the-art health care will include DNA profiling of the individual cat, and perhaps its tumor, to establish the best treatment approaches. Genetic testing and eventually whole genome sequencing should become routine diagnostics for feline health care.

GLOBAL IMPORTANCE

Cat breeds have disseminated around the world. Thus, practitioners should be aware of the breeds common to their region and the mutations found in those regional populations. Specific random-bred populations can also have defined genetic characteristics and mutations.

AUDIENCE

This review of 'the good, the bad and the ugly' DNA variants provides the current state of knowledge for genetic testing and genetic health management for cats. It is aimed at feline and general practitioners wanting to update and review the basics of genetics, what tests are available for cats and sources for genetic testing. The tables are intended to be used as references in the clinic. Practitioners with a high proportion of cat breeder clientele will especially benefit from the review.

EVIDENCE BASE

The data presented is extracted from peer-reviewed publications pertaining to mutation identification, and relevant articles concerning the heritable trait and/or disease. The author also draws upon personal experience and expertise in feline genetics.

Genetics of Pigmentation in Dogs and Cats

Color variation in companion animals has long been of interest to the breeding and scientific communities. Simple traits, like black versus brown or yellow versus black, have helped to explain principles of transmission genetics and continue to serve as models for studying gene action and interaction. We present a molecular genetic review of pigmentary variation in dogs and cats using a nomenclature and logical framework established by early leaders in the field. For most loci in which molecular variants have been identified (nine in dogs and seven in cats), homologous mutations exist in laboratory mice and/or humans. Exceptions include the K locus in dogs and the Tabby locus in cats, which give rise to alternating stripes or marks of different color, and which illustrate the continued potential of coat color genetics to provide insight into areas that transcend pigment cell biology.

Genetic testing in domestic cats

Varieties of genetic tests are currently available for the domestic cat that support veterinary health care, breed management, species identification, and forensic investigations. Approximately thirty-five genes contain over fifty mutations that cause feline health problems or alterations in the cat's appearance. Specific genes, such as sweet and drug receptors, have been knocked-out of Felidae during evolution and can be used along with mtDNA markers for species identification. Both STR and SNP panels differentiate cat race, breed, and individual identity, as well as gender-specific markers to determine sex of an individual. Cat genetic tests are common offerings for commercial laboratories, allowing both the veterinary clinician and the private owner to obtain DNA test results. This article will review the genetic tests for the domestic cat, and their various applications in different fields of science. Highlighted are genetic tests specific to the individual cat, which are a part of the cat's genome.

Defining and mapping mammalian coat pattern genes: multiple genomic regions implicated in domestic cat stripes and spots

Mammalian coat patterns (e.g., spots, stripes) are hypothesized to play important roles in camouflage and other relevant processes, yet the genetic and developmental bases for these phenotypes are completely unknown. The domestic cat, with its diversity of coat patterns, is an excellent model organism to investigate these phenomena. We have established three independent pedigrees to map the four recognized pattern variants classically considered to be specified by a single locus, Tabby; in order of dominance, these are the unpatterned agouti form called "Abyssinian" or "ticked" (T(a)), followed by Spotted (T(s)), Mackerel (T(M)), and Blotched (t(b)). We demonstrate that at least three different loci control the coat markings of the domestic cat. One locus, responsible for the Abyssinian form (herein termed the Ticked locus), maps to an approximately 3.8-Mb region on cat chromosome B1. A second locus controls the Tabby alleles T(M) and t(b), and maps to an approximately 5-Mb genomic region on cat chromosome A1. One or more additional loci act as modifiers and create a spotted coat by altering mackerel stripes. On the basis of our results and associated observations, we hypothesize that mammalian patterned coats are formed by two distinct processes: a spatially oriented developmental mechanism that lays down a species-specific pattern of skin cell differentiation and a pigmentation-oriented mechanism that uses information from the preestablished pattern to regulate the synthesis of melanin profiles.

Effects of environmental tobacco smoke in vivo on rhesus monkey semen quality, sperm function, and sperm metabolism

The objective of this study was to use a non-human primate model to examine the effect of environmental tobacco smoke (ETS) in vivo on semen quality, sperm function, and sperm metabolism. Four adult rhesus macaques (Macaca mulatta) were exposed to ETS for six months, and semen samples were collected every week for evaluation. ETS exposure in vivo did not affect semen quality and sperm function. The sperm X:Y chromosome ratio remained unchanged after ETS exposure. The sex ratio of the embryos fertilized by ETS-exposed males was not different from the control male. However, sperm showed changes in metabolome detected by NMR during the ETS exposure. We concluded that with the duration and level of ETS exposure in this study, semen quality and sperm function were not affected, whereas sperm did undergo metabolic changes with ETS exposure in vivo.