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The laminin alpha chains: expression, developmental transitions, and chromosomal locations of alpha1-5, identification of heterotrimeric laminins 8-11, and cloning of a novel alpha3 isoform.

Miner JH, Patton BL, Lentz SI, Gilbert DJ, Snider WD, Jenkins NA, Copeland NG, Sanes JR - J. Cell Biol. (1997)

Bottom Line: Interspecific backcross mapping of the five alpha chain genes revealed that they are distributed on four mouse chromosomes.Finally, we identified a novel full-length alpha3 isoform encoded by the Lama3 gene, which was previously believed to encode only truncated chains.Together, these results reveal remarkable diversity in BL composition and complexity in BL development.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

ABSTRACT
Laminin trimers composed of alpha, beta, and gamma chains are major components of basal laminae (BLs) throughout the body. To date, three alpha chains (alpha1-3) have been shown to assemble into at least seven heterotrimers (called laminins 1-7). Genes encoding two additional alpha chains (alpha4 and alpha5) have been cloned, but little is known about their expression, and their protein products have not been identified. Here we generated antisera to recombinant alpha4 and alpha5 and used them to identify authentic proteins in tissue extracts. Immunoprecipitation and immunoblotting showed that alpha4 and alpha5 assemble into four novel laminin heterotrimers (laminins 8-11: alpha4beta1gamma1, alpha4beta2gamma1, alpha5beta1gamma1, and alpha5beta2gamma1, respectively). Using a panel of nucleotide and antibody probes, we surveyed the expression of alpha1-5 in murine tissues. All five chains were expressed in both embryos and adults, but each was distributed in a distinct pattern at both RNA and protein levels. Overall, alpha4 and alpha5 exhibited the broadest patterns of expression, while expression of alpha1 was the most restricted. Immunohistochemical analysis of kidney, lung, and heart showed that the alpha chains were confined to extracellular matrix and, with few exceptions, to BLs. All developing and adult BLs examined contained at least one alpha chain, all alpha chains were present in multiple BLs, and some BLs contained two or three alpha chains. Detailed analysis of developing kidney revealed that some individual BLs, including those of the tubule and glomerulus, changed in laminin chain composition as they matured, expressing up to three different alpha chains and two different beta chains in an elaborate and dynamic progression. Interspecific backcross mapping of the five alpha chain genes revealed that they are distributed on four mouse chromosomes. Finally, we identified a novel full-length alpha3 isoform encoded by the Lama3 gene, which was previously believed to encode only truncated chains. Together, these results reveal remarkable diversity in BL composition and complexity in BL development.

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The laminin α chain subfamily. Numbering of domains  is based on accepted nomenclature (Sasaki et al., 1988; Engvall  and Wewer, 1996). Numbers of laminin-type cysteine-rich (EGFlike) repeats, rounded to the nearest integer, are indicated within  each domain IIIa, IIIb, or V. Note that laminins α3A and α3B  share domains G, I/II, and IIIa but have distinct NH2 termini.
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Figure 1: The laminin α chain subfamily. Numbering of domains is based on accepted nomenclature (Sasaki et al., 1988; Engvall and Wewer, 1996). Numbers of laminin-type cysteine-rich (EGFlike) repeats, rounded to the nearest integer, are indicated within each domain IIIa, IIIb, or V. Note that laminins α3A and α3B share domains G, I/II, and IIIa but have distinct NH2 termini.

Mentions: The α subfamily of laminin chains currently contains five members. Fig. 1 shows the domain structure of these chains based on the nomenclature of Sasaki et al. (1988). All α chains contain a carboxyl-terminal globular G domain and α-helical domains I and II. The previously described fulllength α1 and α2 chains contain six additional domains (IIIa–VI) that alternate between cysteine-rich stretches containing EGF-like repeats (IIIa, IIIb, and V) and globular regions (IVa, IVb, and VI) (Engvall and Wewer, 1996). The newest member of the family, α5, is also a full-length chain, but it is larger than α1 or α2, owing to the greater number of EGF-like repeats in domain V and a larger domain IVb (Miner et al., 1995). In contrast, laminins α3A and α4 are severely truncated chains that contain only a single cysteine-rich domain (IIIa) downstream of a short aminoterminal domain (Ryan et al., 1994; Galliano et al., 1995; Iivanainen et al., 1995; Richards et al., 1996). Of the vertebrate α chains, α5 may be most like the ancestral α chain, because of its similarity in both domain structure and sequence to the only known invertebrate α chain, Drosophila A (Miner et al., 1995).


The laminin alpha chains: expression, developmental transitions, and chromosomal locations of alpha1-5, identification of heterotrimeric laminins 8-11, and cloning of a novel alpha3 isoform.

Miner JH, Patton BL, Lentz SI, Gilbert DJ, Snider WD, Jenkins NA, Copeland NG, Sanes JR - J. Cell Biol. (1997)

The laminin α chain subfamily. Numbering of domains  is based on accepted nomenclature (Sasaki et al., 1988; Engvall  and Wewer, 1996). Numbers of laminin-type cysteine-rich (EGFlike) repeats, rounded to the nearest integer, are indicated within  each domain IIIa, IIIb, or V. Note that laminins α3A and α3B  share domains G, I/II, and IIIa but have distinct NH2 termini.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139892&req=5

Figure 1: The laminin α chain subfamily. Numbering of domains is based on accepted nomenclature (Sasaki et al., 1988; Engvall and Wewer, 1996). Numbers of laminin-type cysteine-rich (EGFlike) repeats, rounded to the nearest integer, are indicated within each domain IIIa, IIIb, or V. Note that laminins α3A and α3B share domains G, I/II, and IIIa but have distinct NH2 termini.
Mentions: The α subfamily of laminin chains currently contains five members. Fig. 1 shows the domain structure of these chains based on the nomenclature of Sasaki et al. (1988). All α chains contain a carboxyl-terminal globular G domain and α-helical domains I and II. The previously described fulllength α1 and α2 chains contain six additional domains (IIIa–VI) that alternate between cysteine-rich stretches containing EGF-like repeats (IIIa, IIIb, and V) and globular regions (IVa, IVb, and VI) (Engvall and Wewer, 1996). The newest member of the family, α5, is also a full-length chain, but it is larger than α1 or α2, owing to the greater number of EGF-like repeats in domain V and a larger domain IVb (Miner et al., 1995). In contrast, laminins α3A and α4 are severely truncated chains that contain only a single cysteine-rich domain (IIIa) downstream of a short aminoterminal domain (Ryan et al., 1994; Galliano et al., 1995; Iivanainen et al., 1995; Richards et al., 1996). Of the vertebrate α chains, α5 may be most like the ancestral α chain, because of its similarity in both domain structure and sequence to the only known invertebrate α chain, Drosophila A (Miner et al., 1995).

Bottom Line: Interspecific backcross mapping of the five alpha chain genes revealed that they are distributed on four mouse chromosomes.Finally, we identified a novel full-length alpha3 isoform encoded by the Lama3 gene, which was previously believed to encode only truncated chains.Together, these results reveal remarkable diversity in BL composition and complexity in BL development.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

ABSTRACT
Laminin trimers composed of alpha, beta, and gamma chains are major components of basal laminae (BLs) throughout the body. To date, three alpha chains (alpha1-3) have been shown to assemble into at least seven heterotrimers (called laminins 1-7). Genes encoding two additional alpha chains (alpha4 and alpha5) have been cloned, but little is known about their expression, and their protein products have not been identified. Here we generated antisera to recombinant alpha4 and alpha5 and used them to identify authentic proteins in tissue extracts. Immunoprecipitation and immunoblotting showed that alpha4 and alpha5 assemble into four novel laminin heterotrimers (laminins 8-11: alpha4beta1gamma1, alpha4beta2gamma1, alpha5beta1gamma1, and alpha5beta2gamma1, respectively). Using a panel of nucleotide and antibody probes, we surveyed the expression of alpha1-5 in murine tissues. All five chains were expressed in both embryos and adults, but each was distributed in a distinct pattern at both RNA and protein levels. Overall, alpha4 and alpha5 exhibited the broadest patterns of expression, while expression of alpha1 was the most restricted. Immunohistochemical analysis of kidney, lung, and heart showed that the alpha chains were confined to extracellular matrix and, with few exceptions, to BLs. All developing and adult BLs examined contained at least one alpha chain, all alpha chains were present in multiple BLs, and some BLs contained two or three alpha chains. Detailed analysis of developing kidney revealed that some individual BLs, including those of the tubule and glomerulus, changed in laminin chain composition as they matured, expressing up to three different alpha chains and two different beta chains in an elaborate and dynamic progression. Interspecific backcross mapping of the five alpha chain genes revealed that they are distributed on four mouse chromosomes. Finally, we identified a novel full-length alpha3 isoform encoded by the Lama3 gene, which was previously believed to encode only truncated chains. Together, these results reveal remarkable diversity in BL composition and complexity in BL development.

Show MeSH
Related in: MedlinePlus