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The genetic control of hair growth has been studied in mice carrying the following coat texture genes: fz (fuzzy), soc (soft coat), hid (hair interior defect), sa (satin), It (lustrous), Ve (velvet), wa-1 (waved-1), Re (rex), Rewc (wavy coat) and pk (plucked).

A general effect on cells of epidermal origin, found in soc/soc and Ve/+ skin samples illustrates how common factors control developmental potential in both the stratum germinativum and the follicle bulb. A direct influence on follicle bulb development is also seen in fz/fz homozygotes in which the dermal papilla functions abnormally. The role of the bulb cells and the dermal papilla in the control of hair shaft calibre is discussed.

hid is a new gene, found in homozygous condition in all mice of the AKR inbred strain. hid and sa appear primarily to be concerned in the differentiation of the medulla.

In the hair waving mutants, waved-1, rex and wavy coat, the processes controlling hair movement within the follicle are disturbed. These genes appear to regulate internal root sheath function. When the normal relationship between internal root sheath and developing hair shaft is disturbed, shaft movement slows, with the subsequent development of shaft calibre abnormalities.

pk acts at the level of the sebaceous gland, disturbing the normal process of hair eruption. The roles of the internal root sheath, external root sheath and the sebaceous gland in hair eruption are discussed.

The abnormal epidermal layer in soc/soc and Ve/+ skin also disturbs hair eruption to a small extent. The resulting abnormalities this causes in hair shaft formation are compared with those found pk/pk samples and also with the similar effects of faulty hair movement in the hair waving mutants. An effect on pigmentation is also described.

The chemistry of keratinization appears to be normal in all these mutants.