The Adult Murine Intestine is Dependent on Constitutive Laminin-?1 Synthesis.
ABSTRACT: Laminin-?1 is required for early embryonic development; however, the need for laminin-?1 synthesis in adulthood is unknown. A global and inducible mouse model of laminin-?1 deficiency was generated to address this question. Genetic ablation of the Lamc1 gene in adult mice was rapidly lethal. Despite global Lamc1 gene deletion in tamoxifen-induced mutant mice, there was minimal change in total cardiac, pulmonary, hepatic or renal laminin protein. In contrast, laminin-?1 was significantly depleted in the small intestines, which showed crypt hyperplasia and dissociation of villous epithelium from adjacent mesenchyme. We conclude that the physiologic requirement for laminin-?1 synthesis in adult mice is dependent on a tissue-specific basal rate of laminin-?1 turnover that results in rapid depletion of laminin-?1 in the intestine.
Project description:Laminin-integrin interactions regulate various adhesion-dependent cellular processes. ?1C-Glu, the Glu residue in the laminin ?1 chain C-terminal tail, is crucial for the binding of ?1-laminins to several integrin isoforms. Here, we investigated the impact of ?1C Glu to Gln mutation on ?1-laminin binding to all possible integrin partners in vitro, and found that the mutation specifically ablated binding to ?3, ?6, and ?7 integrins. To examine the physiological significance of ?1C-Glu, we generated a knock-in allele, Lamc1 EQ , in which the ?1C Glu to Gln mutation was introduced. Although Lamc1 EQ/EQ homozygotes developed into blastocysts and deposited laminins in their basement membranes, they died just after implantation because of disordered extraembryonic development. Given the impact of the Lamc1 EQ allele on embryonic development, we developed a knock-in mouse strain enabling on-demand introduction of the ?1C Glu to Gln mutation by the Cre-loxP system. The present study has revealed a crucial role of ?1C-Glu-mediated integrin binding in postimplantation development and provides useful animal models for investigating the physiological roles of laminin-integrin interactions in vivo.
Project description:Molecular markers associated with tumor progression in uterine carcinoma are poorly defined. In this study, we determine whether upregulation of LAMC1, a gene encoding extracellular matrix protein, laminin ?1, is associated with various uterine carcinoma subtypes and stages of tumor progression.An analysis of the immunostaining patterns of laminin ?1 in normal endometrium, atypical hyperplasia, and a total of 150 uterine carcinomas, including low-grade and high-grade endometrioid carcinomas, uterine serous and clear cell carcinoma, was performed. Clinicopathological correlation was performed to determine biological significance. The Cancer Genome Atlas (TCGA) data set was used to validate our results.As compared to normal proliferative and secretory endometrium, for which laminin ?1 immunoreactivity was almost undetectable, increasing laminin C1 staining intensity was observed in epithelial cells from atypical hyperplasia to low-grade endometrioid to high-grade endometrioid carcinoma, respectively. Laminin ?1 expression was significantly associated with FIGO stage, myometrial invasion, cervical/adnexal involvement, angiolymphatic invasion and lymph node metastasis. Similarly, analysis of the endometrial carcinoma data set from TCGA revealed that LAMC1 transcript levels were higher in high-grade than those in low-grade endometrioid carcinoma. Silencing LAMC1 expression by siRNAs in a high-grade endometrioid carcinoma cell line did not affect its proliferative activity but significantly suppressed cell motility and invasion in vitro.These data suggest that laminin ?1 may contribute to the development and progression of uterine carcinoma, likely through enhancing tumor cell motility and invasion. Laminin ?1 warrants further investigation regarding its role as a biomarker and therapeutic target in uterine carcinoma.
Project description:It has been suggested that there are histological and functional distinctions between the periodontal ligament (PDL) of deciduous (DecPDL) and permanent (PermPDL) teeth. Thus, we hypothesized that DecPDL and PermPDL display differences in the constitutive expression of genes/proteins involved with PDL homeostasis. Primary PDL cell cultures were obtained for DecPDL (n = 3) and PermPDL (n = 3) to allow us to perform label-free quantitative secretome analysis. Although a highly similar profile was found between DecPDL and PermPDL cells, comparative secretome analysis evidenced that one of the most stickling differences involved cell adhesion molecules, including laminin subunit gamma 1 (LAMC1) and beta 2 (LAMB2). Next, total RNA and protein extracts were obtained from fresh PDL tissues of deciduous (n = 6) and permanent (n = 6) teeth, and Western blotting and qPCR analysis were used to validate our in vitro findings. Western blot analysis confirmed that LAMC1 was increased in DecPDL fresh tissues (p<0.05). Furthermore, qPCR data analysis revealed that mRNA levels for laminin subunit beta 1 (LAMB1), beta 3 (LAMB3), LAMC1, and gamma 2 (LAMC2) were higher in DecPDL fresh tissues, whereas transcripts for LAMB2 were increased in PermPDL (p<0.05). In conclusion, the differential expression of laminin chains in DecPDL and PermPDL suggests an involvement of laminin-dependent pathways in the control of physiological differences between them.
Project description:There is compelling evidence to suggest that serous tubal intraepithelial carcinoma (STIC) is the likely primary site for the development of many pelvic high-grade serous carcinomas (HGSCs). Identifying molecules that are upregulated in STIC is important not only to provide biomarkers to assist in the diagnosis of STIC but also to elucidate our understanding of the pathogenesis of HGSC. In this study, we performed RNA sequencing to compare transcriptomes between HGSC and normal fallopian tube epithelium (FTE), and we identified LAMC1 encoding laminin ?1 as one of the preferentially upregulated genes associated with HGSC. Reverse transcription polymerase chain reaction further validated LAMC1 upregulation in HGSC as compared with normal FTE. Immunohistochemical analysis was performed on 32 cases of concurrent HGSC and STIC. The latter was diagnosed on the basis of morphology, TP53 mutations, and p53 and Ki-67 immunohistochemical patterns. Laminin ?1 immunostaining intensity was found to be significantly higher in STIC and HGSC compared with adjacent FTE in all cases (P<0.001). In normal FTE, laminin ?1 immunoreactivity was predominantly localized in the basement membrane or on the apical surface of ciliated cells, whereas in STIC and HGSC cells, laminin ?1 staining was diffuse and intense throughout the cytoplasm. More importantly, strong laminin ?1 staining was detected in all 13 STICs, which lacked p53 immunoreactivity because of null mutations. These findings suggest that the overexpression of laminin ?1 immunoreactivity and alteration of its staining pattern in STICs can serve as a useful tissue biomarker, especially for those STICs that are negative for p53 and have a low Ki-67 labeling index.
Project description:Laminins promote early stages of peripheral nerve myelination by assembling basement membranes (BMs) on Schwann cell surfaces, leading to activation of ?1 integrins and other receptors. The BM composition, structural bonds and ligands needed to mediate this process, however, are not well understood. Mice hypomorphic for laminin ?1-subunit expression that assembled endoneurial BMs with reduced component density exhibited an axonal sorting defect with amyelination but normal Schwann cell proliferation, the latter unlike the null. To identify the basis for this, and to dissect participating laminin interactions, LAMC1 gene-inactivated dorsal root ganglia were treated with recombinant laminin-211 and -111 lacking different architecture-forming and receptor-binding activities, to induce myelination. Myelin-wrapping of axons by Schwann cells was found to require higher laminin concentrations than either proliferation or axonal ensheathment. Laminins that were unable to polymerize through deletions that removed critical N-terminal (LN) domains, or that lacked cell-adhesive globular (LG) domains, caused reduced BMs and almost no myelination. Laminins engineered to bind weakly to ?6?1 and/or ?7?1 integrins through their LG domains, even though they could effectively assemble BMs, decreased myelination. Proliferation depended upon both integrin binding to LG domains and polymerization. Collectively these findings reveal that laminins integrate scaffold-forming and cell-adhesion activities to assemble an endoneurial BM, with myelination and proliferation requiring additional ?6?1/?7?1-laminin LG domain interactions, and that a high BM ligand/structural density is needed for efficient myelination.
Project description:Insulin-like growth factor-binding protein-5 (IGFBP-5) has IGF-1-independent intranuclear effects that are poorly defined. Treatment of cells with IGFBP-5 induces migration, prevents apoptosis, and leads to increased laminin subunit transcription. Similarly, filamin A (FLNa), an actin-binding protein that participates in cell attachment, plays important additional roles in signal transduction and modulation of transcriptional responses. In this report, we show that IGFBP-5 leads to dephosphorylation of FLNa with subsequent FLNa cleavage. Following cleavage, there is enhanced recruitment of Smad3/4 to a C-terminal FLNa fragment with nuclear translocation and subsequent binding to the promoter region of the laminin gamma1 (lamc1) gene. FLNa knockdown prevents IGFBP-5-mediated increases in lamc1 transcription. These data indicate that IGFBP-5 induces formation of a FLNa-based nuclear shuttle that recruits transcription factors and regulates transcription of IGFBP-5 target genes. These studies provide new insights into the mechanisms whereby IGFBP-5 and FLNa exert intranuclear effects.
Project description:In order to understand the functions of laminins in the renal collecting system, the Lamc1 gene was inactivated in the developing mouse ureteric bud (UB). Embryos bearing null alleles exhibited laminin deficiency prior to mesenchymal tubular induction and either failed to develop a UB with involution of the mesenchyme, or developed small kidneys with decreased proliferation and branching, delayed renal vesicle formation and postnatal emergence of a water transport deficit. Embryonic day 12.5 kidneys revealed an almost complete absence of basement membrane proteins and reduced levels of ?6 integrin and FGF2. mRNA levels for fibroblast growth factor 2 (FGF2) and mediators of the GDNF/RET and WNT11 signaling pathway were also decreased. Furthermore, collecting duct cells derived from laminin-deficient kidneys and grown in collagen gels were found to proliferate and branch slowly. The laminin-deficient cells exhibited decreased activation of growth factor- and integrin-dependent pathways, whereas heparin lyase-treated and ?1 integrin-null cells exhibited more selective decreases. Collectively, these data support a requirement of ?1 laminins for assembly of the collecting duct system basement membrane, in which immobilized ligands act as solid-phase agonists to promote branching morphogenesis, growth and water transport functions.
Project description:Astrocytes express laminin and assemble basement membranes (BMs) at their endfeet, which ensheath the cerebrovasculature. The function of astrocytic laminin in cerebrovascular integrity is unknown. We show that ablation of astrocytic laminin by tissue-specific Cre-mediated recombination disrupted endfeet BMs and led to hemorrhage in deep brain regions of adult mice, resembling human hypertensive hemorrhage. The lack of astrocytic laminin led to impaired function of vascular smooth muscle cells (VSMCs), where astrocytes have a closer association with VSMCs in small arterioles, and was associated with hemorrhagic vessels, which exhibited VSMC fragmentation and vascular wall disassembly. Acute disruption of astrocytic laminin in the striatum of adult mice also impaired VSMC function, indicating that laminin is necessary for VSMC maintenance. In vitro, both astrocytes and astrocytic laminin promoted brain VSMC differentiation. These results show that astrocytes regulate VSMCs and vascular integrity in small vessels of deep brain regions. Therefore, astrocytes may be a possible target for hemorrhagic stroke prevention and therapy.
Project description:Mutations in LAMA2, the gene for the extracellular matrix protein laminin-alpha2, cause a severe muscular dystrophy termed congenital muscular dystrophy type-1A (MDC1A). MDC1A patients have accompanying CNS neural dysplasias and white matter abnormalities for which the underlying mechanisms remain unknown. Here, we report that in laminin-deficient mice, oligodendrocyte development was delayed such that oligodendrocyte progenitors accumulated inappropriately in adult brains. Conversely, laminin substrates were found to promote the transition of oligodendrocyte progenitors to newly formed oligodendrocytes. Laminin-enhanced differentiation was Src family kinase-dependent and resulted in the activation of the Src family kinase Fyn. In laminin-deficient brains, however, increased Fyn repression was accompanied by elevated levels of the Src family kinase negative regulatory proteins, Csk (C-terminal Src kinase), and its transmembrane adaptor, Cbp (Csk-binding protein). These findings indicate that laminin deficiencies delay oligodendrocyte maturation by causing dysregulation of signaling pathways critical for oligodendrocyte development, and suggest that a normal role for CNS laminin is to promote the development of oligodendrocyte progenitors into myelin-forming oligodendrocytes via modulation of Fyn regulatory molecules.
Project description:The mammalian intestine displays two distinct patterns of mucosal organization. The small intestine contains mucosal epithelial invaginations (the crypts of Lieberkühn) that are continuous with evaginations (villi) into the lumen. The colon also contains crypts of Lieberkühn, but its epithelial surface is lined by flat surface cuffs. The epithelial cells of both organs communicate with the underlying mesenchyme through a basement membrane that is composed of a variety of extracellular matrix proteins, including members of the laminin family. The basement membranes of the small intestine and colon contain distinct laminin subtypes; notably, the villus basement membrane is rich in laminin alpha 5. Here, we show that the diminution of laminin alpha 5 in a mouse model led to a compensatory deposition of colonic laminins, which resulted in a transformation from a small intestinal to a colonic mucosal architecture. The alteration in mucosal architecture was associated with reduced levels of nuclear p27Kip1 - a cell-cycle regulator - and altered intestinal epithelial cell proliferation, migration and differentiation. Our results suggest that laminin alpha 5 has a crucial role in establishing and maintaining the specific mucosal pattern of the mouse small intestine.