Alternative titles; symbolsMAMMAGLOBIN 2; MGB2MAMMAGLOBIN BLACRYGLOBINLIPOPHILIN C; LPNCHGNC Approved Gene Symbol: SCGB2A1Cytogenetic location: 11q12.3 Genom...
Alternative titles; symbols
HGNC Approved Gene Symbol: SCGB2A1
Cytogenetic location: 11q12.3 Genomic coordinates (GRCh38): 11:62,208,672-62,213,942 (from NCBI)
Members of the secretoglobin family, such as SCGB2A1, are secreted proteins of about 10 kD that are found in high concentrations in fluids of lung, lacrimal gland, salivary gland, prostate, uterus, and other tissues. Secretoglobins form stable dimers prior to secretion (summary by Jackson et al., 2011).
▼ Cloning and Expression
The uteroglobin gene family includes the uteroglobin (UGB; 192020) and mammaglobin (MGB) genes. By screening a human genomic library with an MGB gene fragment, Becker et al. (1998) isolated a segment of a novel gene showing high sequence similarity to MGB. Based on this similarity, they named the novel gene mammaglobin B, which is also called mammaglobin-2 (MGB2). The authors isolated a full-length MGB2 cDNA by RACE PCR using mRNA from a human breast cancer cell line. The predicted 95-amino acid MGB2 protein contains the conserved residues characteristic of the uteroglobin family. MGB2 shares 58% amino acid sequence identity with MGB and 23% identity with UGB. Becker et al. (1998) found that MGB2 is identical to a 68-amino acid peptide of lacryglobin, a human tear protein identified and sequenced by Molloy et al. (1997), except that MGB2 contains 18 additional amino acids at the N terminus and 9 additional amino acids at the C terminus. Becker et al. (1998) suggested that the 18 N-terminal amino acids are cleaved prior to secretion from the lacrimal gland and that the 9 amino acids at the C terminus represent amino acids not identified in the lacryglobin fragment sequenced. RNA dot blot analysis found MGB2 expression in normal human breast, uterus, and salivary gland, but not in prostate or stomach. Northern blot analysis detected MGB2 expression in normal breast and breast tumor samples, with an apparent overexpression in tumor samples compared with patient-matched normal samples. Northern blot analysis of uterus samples showed MGB2 expression in 2 of 8 normal samples and 2 of 8 tumor samples.
Zhao et al. (1999) cloned SCGB2A1, which they called lipophilin C, from a human lacrimal gland cDNA library. The deduced 95-amino acid prelipophilin C protein has a calculated molecular mass of 10.9 kD. Removal of the N-terminal signal sequence yields a mature 77-amino acid protein with a predicted molecular mass of 8.9 kD. RT-PCR detected lipophilin C expression in thymus, prostate, testis, salivary gland, kidney, trachea, uterus, mammary gland, ovary, and lacrimal gland. Little to no expression was present in skeletal muscle, small intestine, spleen, placenta, bone marrow, and leukocytes.
▼ Gene Structure
Becker et al. (1998) determined that the MGB2 gene contains 3 exons.
By FISH, Becker et al. (1998) mapped the MGB2 gene to 11q13, which is where the MGB and UGB genes are located. Independently, Zhao et al. (1999) mapped the SCGB2A1 gene to chromosome 11q12-q13.1 using FISH.