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The nuclear lamina consists of two components, lamins and nuclear lamin-associated membrane proteins. The lamins are type V intermediate filaments which can be categorized as either A-type (lamin A, C) or B-type (lamin B 1, B 2) according to homology of their DNA sequences, biochemical properties and cellular localization during the cell cycle.
Nuclear lamins interact with inner nuclear membrane proteins to form the nuclear lamina on the interior of the nuclear envelope. Lamins have elastic and mechanosensitive properties, and can alter gene regulation in a feedback response to mechanical cues. [1] Lamins are present in all animals but are not found in microorganisms, plants or fungi.
The nuclear envelope is made up of two lipid bilayer membranes, an inner nuclear membrane and an outer nuclear membrane. These membranes are connected to each other by nuclear pores. Two sets of intermediate filaments provide support for the nuclear envelope. An internal network forms the nuclear lamina on the inner nuclear membrane. [7]
Rexed never described this as lamina X but as area X. [7] Anterior grey column: VIII–IX Lamina VIII: motor interneurons; Lamina IX: hypaxial (body wall muscles), lateral (in limb regions) and medial (back muscles) motor neurons, also phrenic and spinal accessory nuclei at cervical levels, and Onuf's nucleus in the sacral region
Laminins were previously numbered as they were discovered, i.e., laminin-1, laminin-2, laminin-3, etc., but the nomenclature was changed to describe which chains are present in each isoform (laminin-111, laminin-211, etc.). [3] In addition, many laminins had common names before either laminin nomenclature was in place. [7] [8]
Lamin proteins are thought to be involved in nuclear stability, chromatin structure, and gene expression. Vertebrate lamins consist of two types, A and B. This gene encodes one of the two B type proteins, B1. [7] Lamin B, along with heterochromatin, is anchored to the inner surface of the nuclear membrane by the lamin B receptor.
The nuclear pore complex (NPC) is a crucial cellular structure with a diameter of approximately 120 nanometers in vertebrates. Its channel varies from 5.2 nanometers in humans [14] to 10.7 nm in the frog Xenopus laevis, with a depth of roughly 45 nm. [15] Additionally, mRNA, being single-stranded, has a thickness ranging from 0.5 to 1 nm.
In contrast to the cytoskeleton, however, the nuclear matrix has been proposed to be a dynamic structure. Along with the nuclear lamina, it supposedly aids in organizing the genetic information within the cell. [1] The exact function of this structure is still disputed, and its very existence has been called into question. [2]