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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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Chromosomal locations of Lama loci in the mouse  genome, as determined from interspecific backcross analysis. The  number of recombinant N2 animals is presented over the total number of N2 animals typed to the left of the chromosome maps between each pair of loci. The recombination frequencies, expressed  as genetic distance in centimorgans (± one standard error) are  also shown. The upper 95% confidence limit of the recombination distance is given in parentheses when no recombinants were  found between loci. Gene order was determined by minimizing  the number of recombination events required to explain the allele distribution patterns. The positions of loci on human chromosomes, where known, are shown to the right of the chromosome maps. (Asterisk) The human LAMA5 gene is predicted to  reside on chromosome 20q13. References for the human map positions of loci cited in this study can be obtained from GDB (Genome Data Base), a computerized database of human linkage information maintained by The William H. Welch Medical Library  of The Johns Hopkins University (Baltimore, MD).
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Figure 11: Chromosomal locations of Lama loci in the mouse genome, as determined from interspecific backcross analysis. The number of recombinant N2 animals is presented over the total number of N2 animals typed to the left of the chromosome maps between each pair of loci. The recombination frequencies, expressed as genetic distance in centimorgans (± one standard error) are also shown. The upper 95% confidence limit of the recombination distance is given in parentheses when no recombinants were found between loci. Gene order was determined by minimizing the number of recombination events required to explain the allele distribution patterns. The positions of loci on human chromosomes, where known, are shown to the right of the chromosome maps. (Asterisk) The human LAMA5 gene is predicted to reside on chromosome 20q13. References for the human map positions of loci cited in this study can be obtained from GDB (Genome Data Base), a computerized database of human linkage information maintained by The William H. Welch Medical Library of The Johns Hopkins University (Baltimore, MD).

Mentions: Backcross mapping refined previously reported chromosomal locations for Lama1–3 and provided the first data on mouse chromosomal locations of Lama4 and Lama5 (Fig. 11). Lama1 has previously been reported to map to the distal region of mouse chromosome 17 in this interspecific backcross (Okazaki et al., 1993; Doyle et al., 1996). Lama2 mapped to the proximal region of mouse chromosome 10, 4.5 centiMorgans (cM) distal of Myb and 3.9 cM proximal of Fyn. This result is in good agreement with previous studies that map Lama2 3.2 ± 1.8 cM distal of Myb on mouse chromosome 10 (Sunada et al., 1994). We have also confirmed the recent results of Aberdam et al. (1994b) and Griffith et al. (1996) by assigning Lama3 to the proximal region of chromosome 18. In our interspecific cross, Lama3 mapped 1.6 cM distal of Tpl1 and 1.1 cM proximal of Cdh2. Lama4 is linked to Lama2 on chromosome 10 and does not recombine with Fyn in 129 animals typed in common, suggesting that the two loci are within 2.3 cM of each other (upper 95% confidence limit). Finally, Lama5 mapped to the very distal region of mouse chromosome 2, 2.2 cM distal of Gnas. Thus, the five Lama loci were distributed on four different mouse autosomes, indicating that most of the Lama genes have become dispersed through evolution.


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)

Chromosomal locations of Lama loci in the mouse  genome, as determined from interspecific backcross analysis. The  number of recombinant N2 animals is presented over the total number of N2 animals typed to the left of the chromosome maps between each pair of loci. The recombination frequencies, expressed  as genetic distance in centimorgans (± one standard error) are  also shown. The upper 95% confidence limit of the recombination distance is given in parentheses when no recombinants were  found between loci. Gene order was determined by minimizing  the number of recombination events required to explain the allele distribution patterns. The positions of loci on human chromosomes, where known, are shown to the right of the chromosome maps. (Asterisk) The human LAMA5 gene is predicted to  reside on chromosome 20q13. References for the human map positions of loci cited in this study can be obtained from GDB (Genome Data Base), a computerized database of human linkage information maintained by The William H. Welch Medical Library  of The Johns Hopkins University (Baltimore, MD).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2139892&req=5

Figure 11: Chromosomal locations of Lama loci in the mouse genome, as determined from interspecific backcross analysis. The number of recombinant N2 animals is presented over the total number of N2 animals typed to the left of the chromosome maps between each pair of loci. The recombination frequencies, expressed as genetic distance in centimorgans (± one standard error) are also shown. The upper 95% confidence limit of the recombination distance is given in parentheses when no recombinants were found between loci. Gene order was determined by minimizing the number of recombination events required to explain the allele distribution patterns. The positions of loci on human chromosomes, where known, are shown to the right of the chromosome maps. (Asterisk) The human LAMA5 gene is predicted to reside on chromosome 20q13. References for the human map positions of loci cited in this study can be obtained from GDB (Genome Data Base), a computerized database of human linkage information maintained by The William H. Welch Medical Library of The Johns Hopkins University (Baltimore, MD).
Mentions: Backcross mapping refined previously reported chromosomal locations for Lama1–3 and provided the first data on mouse chromosomal locations of Lama4 and Lama5 (Fig. 11). Lama1 has previously been reported to map to the distal region of mouse chromosome 17 in this interspecific backcross (Okazaki et al., 1993; Doyle et al., 1996). Lama2 mapped to the proximal region of mouse chromosome 10, 4.5 centiMorgans (cM) distal of Myb and 3.9 cM proximal of Fyn. This result is in good agreement with previous studies that map Lama2 3.2 ± 1.8 cM distal of Myb on mouse chromosome 10 (Sunada et al., 1994). We have also confirmed the recent results of Aberdam et al. (1994b) and Griffith et al. (1996) by assigning Lama3 to the proximal region of chromosome 18. In our interspecific cross, Lama3 mapped 1.6 cM distal of Tpl1 and 1.1 cM proximal of Cdh2. Lama4 is linked to Lama2 on chromosome 10 and does not recombine with Fyn in 129 animals typed in common, suggesting that the two loci are within 2.3 cM of each other (upper 95% confidence limit). Finally, Lama5 mapped to the very distal region of mouse chromosome 2, 2.2 cM distal of Gnas. Thus, the five Lama loci were distributed on four different mouse autosomes, indicating that most of the Lama genes have become dispersed through evolution.

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