High impact information on Lcn5

• The murine epididymis synthesizes and secretes a retinoic acid-binding protein (mE-RABP) that belongs to the lipocalin superfamily [1].
• Transgene and mE-RABP gene expression was detected from 30 days and progressively increased until 60 days of age [1].
• The gene encoding mE-RABP is specifically expressed in the mouse mid/distal caput epididymidis under androgen control [1].
• In transgenic mice, a 5-kilobase pair (kb) promoter fragment, but not a 0.6-kb fragment, of the mE-RABP gene driving the chloramphenicol acetyltransferase (CAT) reporter gene restricted high level of transgene expression to the caput epididymidis [1].
• Murine epididymal retinoic acid-binding protein [or lipocalin 5 (Lcn5)] is synthesized and secreted by the principal cells of the mouse middle/distal caput epididymidis [2].

Biological context of Lcn5

• Here, we reported that the 1.8-kb Lcn5 promoter confers epididymis region-specific gene expression in transgenic mice [2].
• The overall similarity in the primary amino acid sequence of mE-RABP with ESP I and other members of the lipocalin superfamily suggests that they are evolutionarily related [3].
• A complementary DNA encoding the mouse epididymal secretory protein MEP 10 (mouse epididymal protein 10) was cloned and is now renamed murine epididymal retinoic acid binding protein (mE-RABP) [3].
• The analysis of the open reading frame showed that the new gene encoded a putative 17-kDa lipocalin (named mEP17) related to mE-RABP [4].
• A computer analysis of the nucleotide sequence showed the presence of a new gene located 1.7 kb upstream from the mE-RABP gene transcription initiation site [4].

Anatomical context of Lcn5

• Because the mE-RABP gene is specifically expressed in the distal caput, neomycin selection provides a pure population of epithelial cells from that segment [5].
• MEP 10 dissociated completely from caudal spermatozoa under low-salt conditions, indicating that it was not firmly bound to spermatozoa [6].
• MEP 10 immunoreactivity was also seen on the microvilli of the principal cells of the distal caput and corpus and the luminal contents from the distal caput to the cauda epididymidis [7].
• In contrast to MEP 7, there was no detectable MEP 10 immunoreactivity on the organelles of the principal cells involved in protein secretion or endocytosis [7].
• In the case of MEP 7, the gold particles were located on the large supranuclear endocytic vesicles and on some infranuclear lysosomes, from the proximal corpus to the middle cauda, while in the case of MEP 10, gold particles were predominantly present in infranuclear lysosomes from the distal caput to the middle cauda [7].

Associations of Lcn5 with chemical compounds

• A 5-kb promoter fragment of the Lcn5 gene can dictate androgen-dependent and epididymis region-specific gene expression in transgenic mice [2].
• The spatial expression and homology with mE-RABP suggest that mEP17 may act as a retinoid carrier protein within the epididymis. mEP17 mRNA expression disappeared 5 days postcastration [4].

Regulatory relationships of Lcn5

• A murine epididymal retinoic-acid-binding protein (mE-RABP) is specifically expressed in the mid/distal caput epididymidis and is androgen regulated [8].

Other interactions of Lcn5

• The role of forkhead box A2 to restrict androgen-regulated gene expression of lipocalin 5 in the mouse epididymis [2].
• We have previously reported that two lipocalin genes, mERABP (mouse epididymal retinoic acid binding protein), and mEP17 (mouse epididymal protein of 17 kDa), derived from an ancestral gene, are specifically expressed in the epididymis [9].

Analytical, diagnostic and therapeutic context of Lcn5

• Immunolocalization of the CAT protein and in situ hybridization of the corresponding CAT mRNA indicated that transgene expression occurred in the principal cells of the mid/distal caput epididymidis, thereby mimicking the spatial endogenous mE-RABP gene expression [1].
• Androgen replacement, begun 5 days after castration and continued for 4 days restored significant expression of mE-RABP mRNA [3].
• In this report, we have demonstrated by Southern blot analysis of genomic DNA that mE-RABP is encoded by a single-copy gene [10].
• The mE-RABP gene was mapped by fluorescent in situ hybridization to the [A3-B] region of the murine chromosome 2 [10].
• The molecular cloning of the mE-RABP gene completes the characterization of the 20.5-kDa-predicted preprotein leading to the minor and major forms of mE-RABP [10].

References