Puss in Boots stakes her claim, says S.Ananthanarayanan.

While the dog has traditionally been given the first place, the horse and the elephant have also been considered important. And in science and medical research, the mouse and the Guinea pig have held sway.

Leslie A Lyons, from the University of Missouri, however, presents the case of the domestic cat. In an article in the journal, Trends in Genetics, Lyons explains that the cat, apart from having been part of human households since ancient times, is genetically close to humans and a convenient proxy to help discover remedies for human ailments.

The role of the cat in control of vermin is legendary. The cat forms part of the folk tales of all communities, and in Egypt, the cat enjoyed nearly divine status. This is perhaps as the cat has all the traits of its more fearsome relatives, the tigers, lions, cheetahs, leopards and panthers, but has integrated with humans ever since humans stopped being hunter-gatherers and became farmers. And in the US, the article says, a third of households have a pet cat.

The result is that the physiology of the cat is well understood and certainly more deeply studied than that of other domestic animals, “..whether the cat is one of the 10% representing a fancy breed or the 90% representing a randomly bred alley cat,” the article says. The article refers to the database of the “99 Lives Cat Genome Sequencing Consortium,” and how complete genetic information is now available for tracking down a host of genetic diseases that affect cats. And how should this be of interest to humans? For starters, the article says, it was feline leukaemia that showed us the way to understand how cancer develops, and more recently, the COVID-19 drug, remdesvir, was first used to cure peritonitis, a coronavirus-induced fatal disease of cats!

Cat genetics has been of interest since the time of Darwin and has helped decode several genetic puzzles, the article says. One learning being the complexity of genetic pathways and the understanding that all the over 20,000 genes that we have are interrelated. Over 98% of the animal genome, the article says, fall in the ‘dark matter’ zone, of genes that do not code for proteins. And of this, some 10 percent are ‘conserved’ or remain essentially unchanged, over all species, and over the course of evolution. The suggestion is that this conserved portion has a role in regulating how the protein-coding part of the genome acts, leading to the variations of function, biology and physiology, and behaviour and temperament – and interspecies evolution and the characteristics of species and their diseases

In the case of cats, the article says, the chromosomes, or strands of genetic material, are easily told apart, for analysis using the tools of genetic engineering. And the genome of the cat is found to have more collections of genes that are usually inherited together, in common with the human genome, than is the case of other mammals, like mice, rats, dogs or pigs, the article says. The genetic information for the domestic cat, and some other greater cats, is now fully available. And there have been studies of the results of extensive cross breeding, which is feasible between lines of felines. The data thus covers the chromosomes from end to end, and the animal from ‘nose to tail’, the article says.

“Thus, genome-edited cats are feasible, allowing the production of a large animal biomedical model for disease studies, understanding basic biology and physiology, and providing an alternative for long-term model therapeutic trials. New genomic technologies are allowing cats to develop new avenues for understanding evolution, domestication, and adaptation. Feline genomics holds great potential and promise for advancing human medicine and mammalian biology,” the article says.

The article refers to Copy Cat, or Cc, the first cloned cat that was created in 2001. The cell donor had black, orange and white fur, but the kitten did not have any orange fur. This ran against Mendel’s laws and basic genetics, and was an indicator that there was more to heredity and genetics that we were aware of.

Speaking of the coloration of cat coats, there is a paper this week in the journal, Nature Communications, where Christopher B. Kaelin, Kelly A. McGowan and Gregory S. Barsh, from Hudson Alpha Institute for Biotechnology, Alabama, Stanford University, go into the mechanics how the fur patterns of cats come to be. The question studied, in fact, is wider, of how the cheetah gets its spots and the tiger its stripes (or how the cow’s coat has black and white patches, or even the patterns on the squirrel). The work, however, was carried out on the cat, thanks to ample experimental data and material available through ‘trap-neuter-return’, a programme to control the population of free-roaming cats. And also the data from the database of ’99 Lives Cat Genome Sequencing Consortium’, a collaborative effort coordinated by the Lyons Feline Genetics Laboratory at the University of Missouri.

The question of patterns, or form, in biological organisms, was first studied by the computer scientists and mathematician, Allen Turing, who developed a theory of reaction and diffusion, where waves of chemical agents could generate patterns of form. Further work led to identifying genetic factors that suppress or promote the production of pigments by cells. The current work, reported in Nature Communications, deals with the details of how specific hair cells acquire the message of what colour of hair they would produce.

The team examined non-viable cat embryos, which became available through the ‘trap-neuter-return’ programme, and find that expression of particular genes comes before formation of the skin, and it appears as strip-like variations of skin thickness. A particular protein that regulates the process has been discovered, and the protein is found to have a slightly different form in different lines of cats. And the mechanism may be the same one in the case of other mammals.

The domestic cat, so far regarded only as a catcher of mice and one who purrs and preens, may be our means to understand the complexity of genetics, which lies behind how organisms function in health and sickness.

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