How did hairless rats appear? - briefly
Hairless rats originated from a spontaneous mutation that eliminated fur growth, and researchers subsequently established stable lines through selective breeding for laboratory use. The first recognized strain appeared in the mid‑20th century and has been maintained by propagating the genetic defect.
How did hairless rats appear? - in detail
Hairless laboratory rats originated from spontaneous genetic mutations that disrupted the normal development of hair follicles. The first documented case occurred in the 1970s when a colony of Sprague‑Dawley rats produced a single albino offspring lacking fur. Genetic analysis identified a recessive allele in the Hr (hairless) gene, which interferes with the signaling pathways responsible for keratinocyte differentiation. Breeding this individual with carriers produced a line of homozygous hairless rats (designated “HR” or “nude” rats).
Researchers then employed targeted breeding strategies to stabilize the trait:
- Backcrossing to eliminate unwanted background mutations while retaining the hairless allele.
- Inbreeding of homozygous individuals to achieve a genetically uniform strain.
- Genotyping using polymerase chain reaction to confirm the presence of the mutant allele in each generation.
The resulting strain exhibits several phenotypic characteristics important for biomedical research:
- Absence of fur, providing unobstructed access to skin and underlying tissues.
- Impaired thermoregulation, requiring controlled ambient temperature and supplemental heating.
- Compromised barrier function, leading to increased susceptibility to infections and necessitating sterile housing conditions.
- Altered immune response, often used to study tumor grafts and wound healing.
Modern techniques have expanded the repertoire of hairless models. CRISPR‑Cas9 editing allows precise disruption of the Hr gene in various rat backgrounds, producing hairless lines without the need for long‑term selective breeding. Additionally, transgenic approaches can combine the hairless phenotype with other genetic modifications, such as fluorescent reporters or disease‑related mutations, creating multifunctional models for dermatology, oncology, and immunology.
In summary, hairless rats emerged from a naturally occurring mutation in the hairless gene, were refined through systematic breeding and genetic verification, and are now generated via genome‑editing technologies to serve specialized experimental purposes.