title: Characterization of hairless (Hr) and FGF5 genes provides insights into the molecular basis of hair loss in cetaceans.
abstract: BACKGROUND
  Hair is one of the main distinguishing characteristics of mammals and it has many important biological functions. Cetaceans originated from terrestrial mammals and they have evolved a series of adaptations to aquatic environments, which are of evolutionary significance. However, the molecular mechanisms underlying their aquatic adaptations have not been well explored. This study provided insights into the evolution of hair loss during the transition from land to water by investigating and comparing two essential regulators of hair follicle development and hair follicle cycling, i.e., the Hairless (Hr) and FGF5 genes, in representative cetaceans and their terrestrial relatives.
  
  
  RESULTS
  The full open reading frame sequences of the Hr and FGF5 genes were characterized in seven cetaceans. The sequence characteristics and evolutionary analyses suggested the functional loss of the Hr gene in cetaceans, which supports the loss of hair during their full adaptation to aquatic habitats. By contrast, positive selection for the FGF5 gene was found in cetaceans where a series of positively selected amino acid residues were identified.
  
  
  CONCLUSIONS
  This is the first study to investigate the molecular basis of the hair loss in cetaceans. Our investigation of Hr and FGF5, two indispensable regulators of the hair cycle, provide some new insights into the molecular basis of hair loss in cetaceans. The results suggest that positive selection for the FGF5 gene might have promoted the termination of hair growth and early entry into the catagen stage of hair follicle cycling. Consequently, the hair follicle cycle was disrupted and the hair was lost completely due to the loss of the Hr gene function in cetaceans. This suggests that cetaceans have evolved an effective and complex mechanism for hair loss.
authors: Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
authors: Zhuo
authors: Z
authors: Chen
authors: Zhengfei
authors: Z
authors: Wang
authors: Shixia
authors: S
authors: Xu
authors: Kaiya
authors: K
authors: Zhou
authors: Guang
authors: G
authors: Yang
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D005075:Biological Evolution; D002591:Cetacea / Q000235:genetics* / Q000502:physiology; D019143:Evolution, Molecular; D005091:Exons; D051521:Fibroblast Growth Factor 5 / Q000235:genetics*; D018859:Hair Follicle; D008958:Models, Molecular; D009154:Mutation; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012641:Selection, Genetic; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D014157:Transcription Factors; D051521:Fibroblast Growth Factor 5
references: Trends Genet. 1992 Feb;8(2):55-61
references: 1566372
references: N Engl J Med. 1999 Aug 12;341(7):491-7
references: 10441606
references: Electrophoresis. 1997 Dec;18(15):2714-23
references: 9504803
references: Mol Endocrinol. 2002 Nov;16(11):2547-60
references: 12403844
references: PLoS One. 2011;6(10):e26579
references: 22046310
references: Mol Biol Evol. 2005 Apr;22(4):1107-18
references: 15689528
references: Science. 1998 Jan 30;279(5351):720-4
references: 9445480
references: Mol Cell Biol. 2002 Oct;22(19):6831-41
references: 12215540
references: BMC Evol Biol. 2009 Jan 25;9:20
references: 19166626
references: Genetics. 2005 Aug;170(4):1459-72
references: 15944362
references: Syst Biol. 2012 Jan;61(1):150-64
references: 21900649
references: Genetics. 1998 Mar;148(3):929-36
references: 9539414
references: J Dermatol Sci. 2007 Dec;48(3):207-11
references: 17869066
references: Nature. 2006 Feb 16;439(7078):811-6
references: 16362057
references: Hum Mol Genet. 1998 Oct;7(11):1671-9
references: 9736769
references: Mol Biol Evol. 2010 Jul;27(7):1467-77
references: 20142439
references: J Biol Chem. 2003 Oct 3;278(40):38665-74
references: 12847098
references: Cell. 1994 Sep 23;78(6):1017-25
references: 7923352
references: Dev Dyn. 1996 Apr;205(4):379-86
references: 8901049
references: Mol Biol Evol. 2002 Jun;19(6):908-17
references: 12032247
references: J Invest Dermatol. 2002 Oct;119(4):920-2
references: 12406339
references: Mol Biol Evol. 2009 Mar;26(3):613-22
references: 19074008
references: Syst Biol. 1999 Mar;48(1):6-20
references: 12078645
references: BMC Bioinformatics. 2010 Jul 15;11:379
references: 20633263
references: Mol Biol Evol. 2007 Aug;24(8):1586-91
references: 17483113
references: Bioinformatics. 2001 Aug;17(8):754-5
references: 11524383
references: Clin Exp Dermatol. 2003 Sep;28(5):535-8
references: 12950347
references: BMC Evol Biol. 2011 Apr 14;11:98
references: 21492470
references: Hum Genet. 1998 Oct;103(4):400-4
references: 9856480
references: Mol Biol Evol. 2005 Mar;22(3):437-55
references: 15509727
references: Yi Chuan. 2008 Jul;30(7):893-9
references: 18779133
references: BMC Evol Biol. 2011 Oct 27;11:314
references: 22029548
references: Mol Biol Evol. 2001 Dec;18(12):2179-85
references: 11719567
references: Exp Dermatol. 1998 Oct;7(5):249-67
references: 9832313
references: J Invest Dermatol. 1999 Dec;113(6):954-9
references: 10594736
references: Nucleic Acids Res. 2003 Jul 1;31(13):3381-5
references: 12824332
references: Proc Natl Acad Sci U S A. 1994 Aug 2;91(16):7717-21
references: 8052649
references: Mol Biol Evol. 1998 May;15(5):568-73
references: 9580986
references: J Cell Biochem. 2010 Jun 1;110(3):671-86
references: 20512927
references: Genetics. 1995 Dec;141(4):1641-50
references: 8601501
references: Bioinformatics. 2006 Jan 15;22(2):195-201
references: 16301204
references: Acta Crystallogr D Biol Crystallogr. 2001 Mar;57(Pt 3):378-84
references: 11223514
references: Mol Phylogenet Evol. 2011 Nov;61(2):255-64
references: 21315162
references: Anim Genet. 2006 Aug;37(4):309-15
references: 16879338
references: J Hered. 2007 Sep-Oct;98(6):555-66
references: 17767004
references: Science. 1990 Jul 13;249(4965):154-7
references: 17836967
references: Mol Biol Evol. 2005 Dec;22(12):2472-9
references: 16107592
references: Nature. 2001 Sep 20;413(6853):277-81
references: 11565023
references: Cytokine Growth Factor Rev. 2005 Apr;16(2):139-49
references: 15863030
references: Nucl Recept Signal. 2009 Dec 31;7:e010
references: 20087431
references: BMC Evol Biol. 2012 Mar 24;12:39
references: 22443485
references: J Invest Dermatol. 2005 Jun;124(6):1200-5
references: 15955095
references: Am J Pathol. 1999 Jul;155(1):159-71
references: 10393848
references: Nucleic Acids Res. 1997 Dec 15;25(24):4876-82
references: 9396791
references: Anim Genet. 2007 Jun;38(3):218-21
references: 17433015
references: Proc Biol Sci. 2012 Nov 7;279(1746):4433-40
references: 22977148