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txmedteach eNotes educator| Certified Educator

To understand the LMNA gene, you need to first recognize what a lamin protein is. These proteins are needed to keep the nuclear envelope intact and make sure it doesn't explode or crumple in on itself. In a way, these proteins act like a skeleton holding the shape of the nucleus intact.

Normally, these proteins are attached to the inner wall of the nucleus, but things change during mitosis. Remember, during mitosis, everything gets divided between the two daughter cells, including what was in the nucleus! To make sure the nucleus can be split, you need to break up the lamins holding it together by phosphorylating them (adding a phosphate group to a certain part of the protein). Once these lamins have been broken off, the nuclear envelope can dissolve and be split between the two new cells.

When you talk about the LMNA gene, itself, you simply need to remember that it is the portion of DNA that encodes a few specific lamin proteins through alternative splicing. In this process, the mRNA created from the gene DNA can be processed in different ways to make different proteins. In other words, the exact same sequence of DNA can yield different proteins, depending on what is going on inside the cell!

There are some obscure medical conditions that result from mutations in the gene, and these specific conditions can be found in the source below, if you would like to see!

myfavouritehero | Student

LMNA is a protein that in humans is encoded by theLMNA gene also known as lamin.

The nuclear lamin consists of a two-dimensional matrix of proteins located next to the inner nuclear membrane. The lamin family of proteins make up the matrix and are highly conserved in evolution. During mitosis, the lamina matrix is reversibly disassembled as the lamin proteins are phosphoylated. Lamin proteins are thought to be involved in nuclear stability, chromatin structure and gene expression. Vertebrate lamins consist of two types, A and B. Through alternate splicing, this gene encodes three type A lamin isoforms.

Early in mitosis, MPF phosphorylates specific serine residues in all three nuclear lamins, causing depolymerization of the lamin intermediate filaments. The phosphorylated lamin B dimers remain associated with the nuclear membrane via their isoprenyl anchor,  Lamin A is targeted to the nuclear membrane by an isoprenyl group but it is cleaved shortly after arriving at the membrane. It stays associated with the membrane through protein-protein interactions of itself and other membrane associated proteins, such as LAP1. Depolymerization of the nuclear lamins leads to disintegration of the nuclear envelope. Transfection experiments demonstrate that phosphorylation of human lamin A is required for lamin depolymerization, and thus for disassembly of the nuclear envelope, which normally occurs early in mitosis.

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