KAL1 gene
Encyclopedia
The KAL1 gene is a human gene
which is located on the X chromosome
at Xp22.3 and is affected in some individuals with Kallmann syndrome
. This gene codes for a protein
named anosmin-1
, which is responsible for migration of certain nerve cell precursors during embryogenesis
. Deletion
or mutation
of this gene results in loss of the functional protein and affects the proper development of the olfactory system
. In addition, neural cells which produce GnRH fail to incorporate into the hypothalamus
.
Clinically, mutation results in the X-linked form of Kallmann syndrome. Individuals with Kallmann syndrome experience anosmia
(lack of smell) and do not go through puberty
(hypothalamic hypogonadotropic hypogonadism).
The KAL1 gene is made of 14 exon
s and spans 120-200 kilobases. Mutation in the gene is responsible for 14% of the cases of familial Kallmann syndrome and 11% of cases of sporadic cases.
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
which is located on the X chromosome
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
at Xp22.3 and is affected in some individuals with Kallmann syndrome
Kallmann syndrome
Kallmann syndrome is a genetic disorder marked by anosmia and hypogonadism - the decreased functioning of the glands that produce sex hormones. Abnormalities in various genes may cause a defect in the hypothalamus, causing a deficiency of gonadotropin-releasing hormone ; this in turn causes...
. This gene codes for a protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
named anosmin-1
Anosmin-1
Anosmin-1 is a secreted, EM associated glycoprotein found in humans and other organisms responsible for normal development, which is expressed in the brain, spinal cord and kidney. Absence or damage to the protein results in Kallmann syndrome in humans, which is characterized by loss of olfactory...
, which is responsible for migration of certain nerve cell precursors during embryogenesis
Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...
. Deletion
Genetic deletion
In genetics, a deletion is a mutation in which a part of a chromosome or a sequence of DNA is missing. Deletion is the loss of genetic material. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome...
or mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
of this gene results in loss of the functional protein and affects the proper development of the olfactory system
Olfactory system
The olfactory system is the sensory system used for olfaction, or the sense of smell. Most mammals and reptiles have two distinct parts to their olfactory system: a main olfactory system and an accessory olfactory system. The main olfactory system detects volatile, airborne substances, while the...
. In addition, neural cells which produce GnRH fail to incorporate into the hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
.
Clinically, mutation results in the X-linked form of Kallmann syndrome. Individuals with Kallmann syndrome experience anosmia
Anosmia
Anosmia is a lack of functioning olfaction, or in other words, an inability to perceive odors. Anosmia may be either temporary or permanent. A related term, hyposmia, refers to a decreased ability to smell, while hyperosmia refers to an increased ability to smell. Some people may be anosmic for one...
(lack of smell) and do not go through puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
(hypothalamic hypogonadotropic hypogonadism).
The KAL1 gene is made of 14 exon
Exon
An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...
s and spans 120-200 kilobases. Mutation in the gene is responsible for 14% of the cases of familial Kallmann syndrome and 11% of cases of sporadic cases.