Laminins are composed of 3 non identical chains: laminin alpha, beta and gamma (formerly A, B1, and B2, respectively) and they form a cruciform structure consisting of 3 short arms, each formed by a different chain, and a long arm composed of all 3 chains. Each laminin chain is a multidomain protein encoded by a distinct gene. Several isoforms of each chain have been described. Different alpha, beta and gamma chain isomers combine to give rise to different heterotrimeric laminin isoforms which are designated by Arabic numerals in the order of their discovery, i.e. alpha1beta1gamma1 heterotrimer is laminin 1. The biological functions of the different chains and trimer molecules are largely unknown, but some of the chains have been shown to differ with respect to their tissue distribution, presumably reflecting diverse functions in vivo.
This gene encodes the alpha chain isoform laminin, alpha 4. The domain structure of alpha 4 is similar to that of alpha 3, both of which resemble truncated versions of alpha 1 and alpha 2, in that approximately 1,200 residues at the N-terminus (domains IV, V and VI) have been lost. Laminin, alpha 4 contains the C-terminal G domain which distinguishes all alpha chains from the beta and gamma chains. The RNA analysis from adult and fetal tissues revealed developmental regulation of expression, however, the exact function of laminin, alpha 4 is not known.[6]
Gene
Tissue-specific utilization of alternative polyA-signal has been described in literature. Also, alternative splicing involving the first intron in the 5' UTR, and laminin alpha 4 like isoforms have been noted, however, the full-length nature of these products is not known.[6]
^"Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^Richards AJ, al-Imara L, Carter NP, Lloyd JC, Leversha MA, Pope FM (Jul 1994). "Localization of the gene (LAMA4) to chromosome 6q21 and isolation of a partial cDNA encoding a variant laminin A chain". Genomics. 22 (1): 237–9. doi:10.1006/geno.1994.1372. PMID7959779.
Iivanainen A, Sainio K, Sariola H, Tryggvason K (May 1995). "Primary structure and expression of a novel human laminin alpha 4 chain". FEBS Letters. 365 (2–3): 183–8. doi:10.1016/0014-5793(95)00462-I. PMID7781776. S2CID83904114.
Burgeson RE, Chiquet M, Deutzmann R, Ekblom P, Engel J, Kleinman H, Martin GR, Meneguzzi G, Paulsson M, Sanes J (Apr 1994). "A new nomenclature for the laminins". Matrix Biology. 14 (3): 209–11. doi:10.1016/0945-053X(94)90184-8. PMID7921537.
Richards A, Luccarini C, Pope FM (Aug 1997). "The structural organisation of LAMA4, the gene encoding laminin alpha4". European Journal of Biochemistry. 248 (1): 15–23. doi:10.1111/j.1432-1033.1997.t01-1-00015.x. PMID9310354.
Mrowiec T, Melchar C, Górski A (1998). "HIV-protein-mediated alterations in T cell interactions with the extracellular matrix proteins and endothelium". Archivum Immunologiae et Therapiae Experimentalis. 45 (2–3): 255–9. PMID9597096.
Fleischmajer R, Kuroda K, Utani A, Douglas MacDonald E, Perlish JS, Arikawa-Hirasawa E, Sekiguchi K, Sanzen N, Timpl R, Yamada Y (Dec 2000). "Differential expression of laminin alpha chains during proliferative and differentiation stages in a model for skin morphogenesis". Matrix Biology. 19 (7): 637–47. doi:10.1016/S0945-053X(00)00092-5. PMID11102753.
McArthur CP, Wang Y, Heruth D, Gustafson S (Jun 2001). "Amplification of extracellular matrix and oncogenes in tat-transfected human salivary gland cell lines with expression of laminin, fibronectin, collagens I, III, IV, c-myc and p53". Archives of Oral Biology. 46 (6): 545–55. doi:10.1016/S0003-9969(01)00014-0. PMID11311202.
Hayashi Y, Kim KH, Fujiwara H, Shimono C, Yamashita M, Sanzen N, Futaki S, Sekiguchi K (Dec 2002). "Identification and recombinant production of human laminin alpha4 subunit splice variants". Biochemical and Biophysical Research Communications. 299 (3): 498–504. doi:10.1016/S0006-291X(02)02642-6. PMID12445830.
