title: LCN6, a novel human epididymal lipocalin.
abstract: BACKGROUND
  The lipocalin (LCN) family of structurally conserved hydrophobic ligand binding proteins is represented in all major taxonomic groups from prokaryotes to primates. The importance of lipocalins in reproduction and the similarity to known epididymal lipocalins prompted us to characterize the novel human epididymal LCN6.
  
  
  RESULTS
  LCN6 cDNA was identified by database analysis in a comprehensive human library sequencing program. Macaca mulatta (rhesus monkey) cDNA was obtained from an epididymis cDNA library and is 93% homologous to the human. The gene is located on chromosome 9q34 adjacent LCN8 and LCN5. LCN6 amino acid sequence is most closely related to LCN5, but the LCN6 beta-barrel structure is best modeled on mouse major urinary protein 1, a pheromone binding protein. Northern blot analysis of RNAs isolated from 25 human tissues revealed predominant expression of a 1.0 kb mRNA in the epididymis. No other transcript was detected except for weak expression of a larger hybridizing mRNA in urinary bladder. Northern hybridization analysis of LCN6 mRNA expression in sham-operated, castrated and testosterone replaced rhesus monkeys suggests mRNA levels are little affected 6 days after castration. Immunohistochemical staining revealed that LCN6 protein is abundant in the caput epithelium and lumen. Immunofluorescent staining of human spermatozoa shows LCN6 located on the head and tail of spermatozoa with the highest concentration of LCN6 on the post-acrosomal region of the head, where it appeared aggregated into large patches.
  
  
  CONCLUSIONS
  LCN6 is a novel lipocalin closely related to Lcn5 and Lcn8 and these three genes are likely products of gene duplication events that predate rodent-primate divergence. Predominant expression in the epididymis and location on sperm surface are consistent with a role for LCN6 in male fertility.
authors: Department of Pediatrics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA. khamil@med.unc.edu
authors: Katherine G
authors: KG
authors: Hamil
authors: Qiang
authors: Q
authors: Liu
authors: P
authors: P
authors: Sivashanmugam
authors: M
authors: M
authors: Anbalagan
authors: Suresh
authors: S
authors: Yenugu
authors: Rama
authors: R
authors: Soundararajan
authors: Gail
authors: G
authors: Grossman
authors: A J
authors: AJ
authors: Rao
authors: Charles E
authors: CE
authors: Birse
authors: Stephen M
authors: SM
authors: Ruben
authors: Richard T
authors: RT
authors: Richardson
authors: Yong-Lian
authors: YL
authors: Zhang
authors: Michael G
authors: MG
authors: O'Rand
authors: Peter
authors: P
authors: Petrusz
authors: Frank S
authors: FS
authors: French
authors: Susan H
authors: SH
authors: Hall
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics; D003001:Cloning, Molecular; D004822:Epididymis / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D054834:Lipocalins; D008253:Macaca mulatta / Q000235:genetics; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009928:Organ Specificity; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; C497171:LCN6 protein, human; D054834:Lipocalins; D012333:RNA, Messenger; D011994:Recombinant Proteins