title: Establishment of a quantitative PCR system for discriminating chitinase-like proteins: catalytically inactive breast regression protein-39 and Ym1 are constitutive genes in mouse lung.
abstract: BACKGROUND
  Mice and humans produce chitinase-like proteins (CLPs), which are highly homologous to chitinases but lack chitinolytic activity. Mice express primarily three CLPs, including breast regression protein-39 (BRP-39) [chitinase 3-like-1 (Chi3l1) or 38-kDa glycoprotein (gp38k)], Ym1 (Chi3l3) and Ym2 (Chi3l4). Recently, CLPs have attracted considerable attention due to their increased expression in a number of pathological conditions, including asthma, allergies, rheumatoid arthritis and malignant tumors. Although the exact functions of CLPs are largely unknown, the significance of their increased expression levels during pathophysiological states needs to be determined. The quantification of BRP-39, Ym1 and Ym2 is an important step in gaining insight into the in vivo regulation of the CLPs.
  
  
  METHODS
  We constructed a standard DNA for quantitative real-time PCR (qPCR) by containing three CLPs target fragments and five reference genes cDNA in a one-to-one ratio. We evaluated this system by analyzing the eight target cDNA sequences. Tissue cDNAs obtained by reverse transcription from total RNA from four embryonic stages and eight adult tissues were analyzed using the qPCR system with the standard DNA.
  
  
  RESULTS
  We established a qPCR system detecting CLPs and comparing their expression levels with those of five reference genes using the same scale in mouse tissues. We found that BRP-39 and Ym1 were abundant in the mouse lung, whereas Ym2 mRNA was abundant in the stomach, followed by lung. The expression levels of BRP-39 and Ym1 in the mouse lung were higher than those of two active chitinases and were comparable to glyceraldehyde-3-phosphate dehydrogenase, a housekeeping gene which is constitutively expressed in all tissues.
  
  
  CONCLUSIONS
  Our results indicate that catalytically inactive BRP-39 and Ym1 are constitutive genes in normal mouse lung.
authors.forename: Misa
authors.initials: M
authors.lastname: Ohno
authors.forename: Yuta
authors.initials: Y
authors.lastname: Kida
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Sakaguchi
authors.forename: Yasusato
authors.initials: Y
authors.lastname: Sugahara
authors.affiliation: Department of Applied Chemistry, Kogakuin University, Hachioji, Tokyo, Japan. f-oyama@cc.kogakuin.ac.jp.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Oyama
mesh_terms: D000818:Animals; D000071451:Chitinase-3-Like Protein 1; D006023:Glycoproteins / Q000235:genetics*; D037102:Lectins / Q000235:genetics*; D008168:Lung / Q000378:metabolism*; D008297:Male; D051379:Mice; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D001619:beta-N-Acetylhexosaminidases / Q000235:genetics*
chemical_list: C509289:Chil1 protein, mouse; D000071451:Chitinase-3-Like Protein 1; D006023:Glycoproteins; D037102:Lectins; D012333:RNA, Messenger; C429541:Chil3 protein, mouse; D001619:beta-N-Acetylhexosaminidases