How did the cat pattern come about

  Recently, the academic journal Nature Communications published a study on the color patterns of cats. This study comes from researchers at the Alpha Institute of Biotechnology in the United States. Unlike the past, researchers have studied the color patterns of cats from the perspective of developmental genetics.
  Complex color patterns are a decisive aspect of the morphological diversity of cats. The study applied morphology and single-cell gene expression analysis to the skin of domestic cat fetuses to determine when, where, and how to establish feline color patterns during fetal development.

The pattern of fetal cat skin epidermis thickening

  The results of this study molecularly understand how leopard spots are formed, suggesting the similar mechanism of periodic color patterns and periodic hair follicle spacing, and identifying targets for different pattern variations in other mammals.
  Understanding the basis of animal color patterns is a long-term concern of development and evolutionary biology. In mammals, markers like cheetah spots and tiger stripes help to inspire theoretical models, such as the Turing reaction diffusion mechanism, which may explain how periodic and stable differences in gene expression and form come from the uniform field of the same cell. produced. Reaction diffusion and other mechanisms that explain periodic morphological structures have involved different developmental processes in laboratory animals, but much less is known about color patterns in mammals. The more prominent examples occur in the natural populations of wild equines and cats, but they are not suitable for genetic or experimental research.
  In fish, color patterns involve direct interactions between pigment cells, which are usually dynamic, allowing additional pattern elements to appear during growth or regeneration. In contrast, in mammalian skin and hair, melanocytes are evenly distributed during development, and the amount and type of melanin are then controlled by paracrine signaling molecules in a single hair follicle.
  In addition, the pattern element characteristics of a single hair follicle, such as the characteristics that produce light or dark hair, remain unchanged during the hair cycle and cell division. Therefore, a single hair spot or streak that is obvious at birth is in the growth process after birth. Scale up. Therefore, the periodic mammalian color pattern can be understood as a process produced by three stages: (1) the establishment of the identity of the pattern element during fetal development; (2) the realization of the pattern through the paracrine signal molecules produced in a single hair follicle Morphology; (3) The maintenance of the identity of model elements in the process of hair circulation and biological growth.
  The “trap-sterilization-release” program has become a popular method to control the excess of wild cats. During the breeding season, about half of all female wildcats are pregnant, and tissue can be extracted from non-living embryos without affecting animal health or interfering with efforts to control the overpopulation of wildcats. Researchers collected more than 200 litters from wild cats and sterilization clinics, and divided a series of developmental stages based on previous studies on cats and laboratory mice.
  Histochemistry and morphological analysis revealed an aspect of epidermal development that has not been described in previous studies. In the 13th stage, the fetal skin is composed of a uniform monolayer of epithelial cells, covering the deficient dermis. About 16 days later, at stage 16, before epidermal differentiation and hair follicle morphogenesis, we noticed that the epidermal tissue was divided into alternate areas of “thick” or “thin”. The characteristics of keratin expression and cell proliferation indicate that thick and thin areas are fundamentally different from the epidermal stratification that usually occurs in the later stages of development. At the 22nd stage, well-developed hair follicles appear, which can be classified according to the type of melanin produced, and a plain pattern is produced: dark spots mainly contain eumelanin, and light areas mainly contain pseudomelanin.
  Domestic cats are useful models for studying color patterns because of their accessibility, genetic and genomic infrastructure, genomic and histological research opportunities for tissue samples, and the diversity of pattern types. The prototype pattern of the tabby cat has regular intervals of dark markings on a light background. The shapes and colors are very different, and many of them are similar to some wild cat species.
  In previous studies on domestic cats, endothelin is the basis of tabby pattern hair follicles, and therefore plays a key role in the realization of tabby pattern17. However, markings are obvious during the development of the hair follicle, which indicates that the establishment of the color pattern must occur during or before the development of the hair follicle.
  Researchers applied single-cell gene expression analysis to the skin of fetal cats to establish the developmental, molecular and genomic basis of the research model. The study revealed an aspect of epidermal development, which marked the establishment of the identity of pattern elements, as well as the characteristics of signal molecules and pathways related to pattern establishment. Studies have found that one of the signal molecules encoded by Dickkopf4 is a naturally occurring mutation that affects the pattern of the tabby and plays a key role in the process of pattern formation.
  This research provides basic insights into the mechanisms by which color patterns are established and provides a platform for broader exploration of the biology of periodic patterns.

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