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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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Immunohistochemical analysis of laminins α1, α4, α5, and γ1 in developing kidney shows the dynamic pattern of α chain accumulation depicted schematically in Fig. 7. All sections are from P1 mouse kidney except c, which is from E15.5. b′, c, d′, f′, g, and h′ are double exposures of doubly labeled sections; antibodies listed first and second are shown in green and red, respectively, and regions of overlap are indicated by yellow and light orange. Single exposure companions are shown in b (for b′), d (for d′), f (for f′), and h (for h′). U,  ureteric bud; V, vesicle; C, comma-shaped structure; S, S-shaped structure; CL, capillary loop; mG, maturing glomerulus; bv, blood vessel. (Arrows) Progenitors of glomerular BL. Bar, 50 μm.
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Figure 8: Immunohistochemical analysis of laminins α1, α4, α5, and γ1 in developing kidney shows the dynamic pattern of α chain accumulation depicted schematically in Fig. 7. All sections are from P1 mouse kidney except c, which is from E15.5. b′, c, d′, f′, g, and h′ are double exposures of doubly labeled sections; antibodies listed first and second are shown in green and red, respectively, and regions of overlap are indicated by yellow and light orange. Single exposure companions are shown in b (for b′), d (for d′), f (for f′), and h (for h′). U, ureteric bud; V, vesicle; C, comma-shaped structure; S, S-shaped structure; CL, capillary loop; mG, maturing glomerulus; bv, blood vessel. (Arrows) Progenitors of glomerular BL. Bar, 50 μm.

Mentions: To search for potential developmental transitions in laminin α chain expression, we stained sections of E15.5 and neonatal mouse kidney with antibodies to laminins α1–5. Results are summarized in Fig. 7 and examples are shown in Fig. 8. Before vesicle formation, the only BL near the cortical surface was that of the ureteric bud. This BL was rich in laminin α5 (Fig. 8 a) throughout its length and also contained α1 (Fig. 8 g) in the cortical portions. The first-formed BL of the nephron, that of the vesicle, contained laminins α1 (not shown) and α4 (Fig. 8 b). Laminin α1 was detected in the BL of some but not all vesicles, suggesting that it appears after α4 near the end of the vesicle stage. In the comma, α1 and α4 remained (Fig. 8, c and e) and were joined by α5 (Fig. 8 a). At this stage, significant heterogeneity became evident within the single BL that surrounded each comma: laminin α4 was present at higher levels in the tuft than in the periphery (Fig. 8 c), whereas laminin α5 was clearly present in the periphery but was virtually absent from the tuft (Fig. 8 a). Thus, the BL of the tuft, which is the precursor of the glomerular BL, becomes molecularly distinct from continuous but nonglomerular stretches of BL at an early stage of nephrogenesis.


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)

Immunohistochemical analysis of laminins α1, α4, α5, and γ1 in developing kidney shows the dynamic pattern of α chain accumulation depicted schematically in Fig. 7. All sections are from P1 mouse kidney except c, which is from E15.5. b′, c, d′, f′, g, and h′ are double exposures of doubly labeled sections; antibodies listed first and second are shown in green and red, respectively, and regions of overlap are indicated by yellow and light orange. Single exposure companions are shown in b (for b′), d (for d′), f (for f′), and h (for h′). U,  ureteric bud; V, vesicle; C, comma-shaped structure; S, S-shaped structure; CL, capillary loop; mG, maturing glomerulus; bv, blood vessel. (Arrows) Progenitors of glomerular BL. Bar, 50 μm.
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Related In: Results  -  Collection

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

Figure 8: Immunohistochemical analysis of laminins α1, α4, α5, and γ1 in developing kidney shows the dynamic pattern of α chain accumulation depicted schematically in Fig. 7. All sections are from P1 mouse kidney except c, which is from E15.5. b′, c, d′, f′, g, and h′ are double exposures of doubly labeled sections; antibodies listed first and second are shown in green and red, respectively, and regions of overlap are indicated by yellow and light orange. Single exposure companions are shown in b (for b′), d (for d′), f (for f′), and h (for h′). U, ureteric bud; V, vesicle; C, comma-shaped structure; S, S-shaped structure; CL, capillary loop; mG, maturing glomerulus; bv, blood vessel. (Arrows) Progenitors of glomerular BL. Bar, 50 μm.
Mentions: To search for potential developmental transitions in laminin α chain expression, we stained sections of E15.5 and neonatal mouse kidney with antibodies to laminins α1–5. Results are summarized in Fig. 7 and examples are shown in Fig. 8. Before vesicle formation, the only BL near the cortical surface was that of the ureteric bud. This BL was rich in laminin α5 (Fig. 8 a) throughout its length and also contained α1 (Fig. 8 g) in the cortical portions. The first-formed BL of the nephron, that of the vesicle, contained laminins α1 (not shown) and α4 (Fig. 8 b). Laminin α1 was detected in the BL of some but not all vesicles, suggesting that it appears after α4 near the end of the vesicle stage. In the comma, α1 and α4 remained (Fig. 8, c and e) and were joined by α5 (Fig. 8 a). At this stage, significant heterogeneity became evident within the single BL that surrounded each comma: laminin α4 was present at higher levels in the tuft than in the periphery (Fig. 8 c), whereas laminin α5 was clearly present in the periphery but was virtually absent from the tuft (Fig. 8 a). Thus, the BL of the tuft, which is the precursor of the glomerular BL, becomes molecularly distinct from continuous but nonglomerular stretches of BL at an early stage of nephrogenesis.

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