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Lamb1

Official Full Name
laminin, beta 1
Background
Laminins, a family of extracellular matrix glycoproteins, are the major noncollagenous constituent of basement membranes. They have been implicated in a wide variety of biological processes including cell adhesion, differentiation, migration, signaling, neurite outgrowth and metastasis. 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 beta chain isoform laminin, beta 1. The beta 1 chain has 7 structurally distinct domains which it shares with other beta chain isomers. The C-terminal helical region containing domains I and II are separated by domain alpha, domains III and V contain several EGF-like repeats, and domains IV and VI have a globular conformation. Laminin, beta 1 is expressed in most tissues that produce basement membranes, and is one of the 3 chains constituting laminin 1, the first laminin isolated from Engelbreth-Holm-Swarm (EHS) tumor. A sequence in the beta 1 chain that is involved in cell attachment, chemotaxis, and binding to the laminin receptor was identified and shown to have the capacity to inhibit metastasis.
Synonyms
LAMB1; laminin, beta 1; CLM, cutis laxa with marfanoid phenotype; laminin subunit beta-1; laminin B1 chain; CLM; MGC142015

Recent Progress

LAMB1 gene encodes laminin beta-1, which is expressed during early development of the human nervous system, and may be involved in the pathogenesis of neurodevelopmental disorders. Scholars also suggested that LAMB1 gene analysis should be considered for intellectually disabled patients with cerebellar cysts, white matter signal change, and cortical malformation.

In one study, researchers aimed to investigate whether single nucleotide polymorphisms (SNPs) in LAMB1 were associated with autism spectrum disorder (ASD) along with related clinical severities of ASD. Results showed that none of the four examined SNPs was associated with ASD risk. However, the genotype of rs2158836 was associated with more severe symptoms. These findings suggested the association between rs2158836 polymorphisms of LAMB1 and symptom severity in ASD.

Cobblestone brain malformation (COB) is a neuronal migration disorder characterized by protrusions of neurons beyond the first cortical layer at the pial surface of the brain. It is usually seen in association with dystroglycanopathy types of congenital muscular dystrophies (CMDs) and ocular abnormalities, also known as muscle-eye-brain disease. Researchers reported homozygous deleterious mutations in LAMB1 in two families with autosomal-recessive COB. Affected individuals displayed a series of brain malformations including cortical gyral and white-matter signal abnormalities, severe cerebellar dysplasia, brainstem hypoplasia, and occipital encephalocele, though with less apparent ocular or muscular abnormalities than typically observed in COB. Given that LAMB1 is localized to the pial basement membrane, there might be a defective connection between radial glial cells and the pial surface mediated by LAMB1 (Fig.1).

Fig. 1. Schematic structure of LAMB1, the encoded protein, position of mutations, and corresponding family number in parentheses. Abbreviations are as follows: LamNT, Laminin N-terminal; LAM IV, Laminin IV type B; EGFLAM, Laminin Epidermal Growth Factor-like domain. (Radmanesh et al, 2013)

Pneumoconiosis is a serious occupational disease worldwide, which is characterized by irreversible and diffuse lung fibrotic lesions. LAMB1 is widely expressed in tissues and is crucial for both lung morphogenesis and physiological function. In another study, investigators explored the association between LAMB1 rs4320486 and risk of pneumoconiosis in a Chinese population, as well as its mechanisms. Regression analysis revealed that individuals with LAMB1 rs4320486 genotypes had a significantly decreased risk of CWP, compared with individuals with CC genotypes. It was shown that the LAMB1 rs4320486 composition could decrease the expression of LAMB1. Compared with normal groups, mRNA levels of LAMB1 were up-regulated in lung tissues of patients with pulmonary fibrosis. Additionally, expressions of LAMB1 were enhanced progressively, along with the development of lung fibrosis. In conclusion, the functional LAMB1 rs4320486 mutation was associated with a decreased risk of CWP in a Chinese population, probably owing to the reduced activity of LAMB1 transcription. LAMB1 expression increased in the progress of lung fibrosis, which suggested that LAMB1 may affect the initiation and progression of pneumoconiosis and serve as a potential biomarker of pneumoconiosis for diagnosis and genetic susceptibility.

The high mortality rate in colorectal cancer is mostly attributed to metastasis, but the only clinical biomarker available for disease monitoring and prognosis is the carcinoembryonic antigen (CEA). However, the prognostic utility of CEA remains controversial. In an effort to identify novel biomarkers that could be potentially translated for clinical use, researchers collected the secretomes from the colon adenocarcinoma cell line HCT-116 and its metastatic derivative E1. Among the glycoproteins, LAMB1 was observed to be over-secreted in E1 cells. In addition, LAMB1 levels were significantly higher in colorectal cancer patient serum samples as compared to healthy controls. Further analysis indicated that LAMB1 performed better than CEA at discriminating between colorectal cancer patients from controls. Moreover, the diagnostic performance was further improved when LAMB1 was used in combination with CEA.

References:

  1. Kim, Y. J., Park, J. K., Kang, W. S., Kim, S. K., Park, H. J., & Nam, M., et al. (2015). Lamb1 polymorphism is associated with autism symptom severity in korean autism spectrum disorder patients. Nordic Journal of Psychiatry, 69(8), 1-5.
  2. Radmanesh, F., Caglayan, A. O., Silhavy, J., Yilmaz, C., Cantagrel, V., & Omar, T., et al. (2013). Mutations in lamb1, cause cobblestone brain malformation without muscular or ocular abnormalities. American Journal of Human Genetics, 92(3), 468-474.
  3. Ji, X., Wu, B., Han, R., Yang, J., Ayaaba, E., & Wang, T., et al. (2017). The association of lamb1 polymorphism and expression changes with the risk of coal workers' pneumoconiosis. Environmental Toxicology, 32(9).
  4. Tonduti, D., Dorboz, I., Renaldo, F., Masliahplanchon, J., Elmalehbergès, M., & Dalens, H., et al. (2015). Cystic leukoencephalopathy with cortical dysplasia related to lamb1 mutations. Neurology, 84(21), 2195-7.
  5. Chen, Q., Lu, G., Cai, Y., Li, Y., Xu, R., & Ke, Y., et al. (2014). Mir-124-5p inhibits the growth of high-grade gliomas through posttranscriptional regulation of lamb1. Neuro-oncology, 16(5), 637.
  6. Lin, Q., Lim, H. S., Lin, H. L., Tan, H. T., Lim, T. K., & Cheong, W. K., et al. (2016). Analysis of colorectal cancer glyco-secretome identifies laminin β-1 (lamb1) as a potential serological biomarker for colorectal cancer. Proteomics, 15(22), 3905-3920.
  7. Okazaki, T., Saito, Y., Hayashida, T., Akaboshi, S., Miyake, N., & Matsumoto, N., et al. (2018). Bilateral cerebellar cysts and cerebral white matter lesions with cortical dysgenesis: expanding the phenotype of lamb1 gene mutations. Clinical Genetics(3).

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