Connexin

As connexins refers to a family of transmembrane proteins that form gap junctions in cells and allow direct exchange of molecules up to a size of about 1 kDa between adjacent cells.

Until now, 21 different connexins of man are known and 20 connexins in the mouse. They vary in size between 23 kDa and 62 kDa. They have four transmembrane domains, two extracellular loops, which are composed of antiparallel β -sheets.

The six connexins accumulate in the membrane to a connexon, which encloses a pore together. Two connexons of two adjacent membranes form a gap junction channel.

There are two different systems for the nomenclature of the connexins. After a nomenclature, the name from the abbreviation Cx and the theoretical molar mass sets (eg Cx43, optionally combined with species abbreviation) together. In another nomenclature connexins are divided into different groups based on their sequence homology.

In the brain, in addition to neurons, the highly specialized glial cells form gap junctions among themselves. Connexin 43 occurs mainly in astrocytes, oligodendrocytes, while connexin 32 mint.

A mutation in the connexin 26 gene is responsible for 11-37 % of all sporadic cases of recessively inherited deafness. Connexin 26 is localized primarily in cell of the inner ear. Since it can store together with connexin 30, this will be included in genetic diagnostics for studies of the mutations by DNA sequencing.