Molecular Responses to Catastrophic Molting in a Wild Marine Mammal

• Main Author: Keith, Anna
• Format: Text
• Language: unknown
• Published: Scholarly Commons 2021
• Subjects: Gene Expression; Genomics; Histology; Molting; Proteomics; Tissue Regeneration; Biology; Life Sciences; Elephant Seals
• Online Access: https://scholarlycommons.pacific.edu/uop_etds/3745; https://scholarlycommons.pacific.edu/cgi/viewcontent.cgi?article=4742&context=uop_etds

While most mammals shed their hair and skin either continuously or seasonally, northern elephant seals (Mirounga angustirostris) undergo an annual catastrophic molt, in which they shed their entire fur and underlying skin layer in the span of just three weeks. Due to the energetic and thermoregulatory constraints of molting and the large distances between their coastal rookeries and foraging grounds, elephant seals must remain on land and fast for the duration of their molt. Previous studies of molting northern elephant seals have examined endocrine and metabolic adjustments to fasting, but not the molecular processes underlying molting. We examined changes in the skin and underlying blubber tissues using histological, endocrine, and proteomic analyses during molting to provide a more in-depth understanding of the cellular mechanisms enabling rapid skin shedding and regeneration in this marine mammal. Shotgun proteome sequencing by LC-MS/MS identified 47,671 peptides and 573 protein groups in skin and outer blubber that were associated with lipid metabolism, protein processing in the endoplasmic reticulum, and collagen regulation. Label-free quantification and differential protein expression analyses identified 23 and 21 proteins that were differentially expressed during molting in the skin and outer blubber, respectively. Proteins downregulated over molting included those associated with inflammation, angiogenesis, and cellular proliferation, whereas proteins upregulated over molting included those associated with cytoskeletal remodeling, collagen synthesis, and lipid metabolism. This suggests that rapid skin regeneration involves intensive protein synthesis and increased vascularization that may be supported by fatty acid substrates from underlying blubber tissue. These data provide insights into cellular and molecular mechanisms that govern unusually rapid skin regeneration in mammals, which may further understanding of disorders affecting the skin and hair of humans and other mammals.