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The official name of this gene is “amyotrophic lateral sclerosis 2 (juvenile).”
ALS2 is the gene's official symbol. The ALS2 gene is also known by other names, listed below.
The ALS2 gene provides instructions for making a protein called alsin. Alsin is produced in a wide range of tissues, with highest amounts in the brain. This protein is particularly abundant in motor neurons, the specialized nerve cells in the brain and spinal cord that control the movement of muscles.
Alsin appears to have many functions, only a few of which are known. Alsin turns on (activates) multiple proteins called GTPases that convert a molecule called GTP into another molecule called GDP. GTPases play important roles in cell division, the process by which cells mature to carry out specific functions (differentiation), and the self-destruction of cells (apoptosis). Alsin is also thought to play a role in cell membrane organization and the transport of molecules from the cell membrane to the interior of the cell (endocytosis). Research findings also suggest that alsin may play a role in the development of axons and dendrites, which are specialized outgrowths from nerve cells that are essential for the transmission of nerve impulses.
The ALS2 gene belongs to a family of genes called ARHGEF (Rho guanine nucleotide exchange factors).
A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.
At least eight mutations in the ALS2 gene have been found to cause amyotrophic lateral sclerosis (ALS), a condition characterized by progressive movement problems and muscle wasting caused by motor neuron death. ALS2 gene mutations are often associated with the juvenile form of ALS, which develops in a person's teens or twenties. Most of these mutations delete single DNA building blocks (nucleotides) in the ALS2 gene, which alters the instructions for producing alsin. As a result of ALS2 gene mutations, alsin does not function correctly or does not function at all.
It is unclear how the loss of functional alsin protein causes ALS. A reduction in alsin function may disrupt the activation of GTPases and prevent the necessary cell functions that they facilitate. Additionally, a lack of functional alsin may impair the movement of essential molecules into cells or alter the development of axons and dendrites. Researchers suggest that the long axons of motor neurons may be particularly sensitive to altered development. It is likely that a combination of these deficits in function eventually cause motor neurons to die, leading to the signs and symptoms of ALS.
Researchers have identified several ALS2 gene mutations that cause infantile-onset ascending hereditary spastic paralysis, a disorder characterized by progressive weakness and stiffness of muscles in the arms, legs, and face that begins within the first 2 years of life. The mutations that cause this condition change or delete one or more nucleotides, which alters the instructions for producing alsin. As a result, alsin is unstable and is broken down rapidly by the cell.
It is unclear how the loss of alsin protein causes infantile-onset ascending hereditary spastic paralysis. Loss of alsin may disrupt the movement of essential molecules within cells or alter the development of axons and dendrites. Long axons are thought to be particularly sensitive to altered development. The loss of functional alsin leads to a decline in motor neuron function causing these nerve cells to die, leading to the signs and symptoms of infantile-onset ascending hereditary spastic paralysis.
Researchers have identified three mutations in the ALS2 gene that cause juvenile primary lateral sclerosis, which is characterized by progressive weakness and stiffness of muscles in the arms, legs, and face that typically begins in childhood. Two of the mutations that cause this disorder delete nucleotides, and one mutation replaces one nucleotide with an incorrect nucleotide. These mutations alter the instructions for producing alsin. As a result, alsin is unstable and is broken down rapidly by the cell, or it is disabled and cannot function properly.
It is unclear how the loss of functional alsin protein causes juvenile primary lateral sclerosis. Loss of alsin may result in a disruption of the movement of molecules within cells or impair the development of axons and dendrites. Researchers suggest that motor neurons and their long axons may be particularly vulnerable to changes in cell development. As a result, motor neuron function declines and eventually these nerve cells die, leading to the signs and symptoms of juvenile primary lateral sclerosis.
Cytogenetic Location: 2q33.1
Molecular Location on chromosome 2: base pairs 201,700,262 to 201,781,171
The ALS2 gene is located on the long (q) arm of chromosome 2 at position 33.1.
More precisely, the ALS2 gene is located from base pair 201,700,262 to base pair 201,781,171 on chromosome 2.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about ALS2 helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
apoptosis ; axons ; cell ; cell division ; cell membrane ; differentiation ; DNA ; endocytosis ; gene ; GTP ; hereditary ; juvenile ; molecule ; motor ; motor neuron ; mutation ; neuron ; nucleotide ; protein ; sclerosis ; wasting
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.