Genes in the ''DLX'' family encode

homeodomain A homeobox is a Nucleic acid sequence, DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. Mutations in a homeobox may change large-scale anatomical features of ...

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...

s related to the ''

Drosophila ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...

'' distal-less ''(Dll)'' gene. The family has been related to a number of developmental features such as jaws and limbs. The family seems to be well preserved across species. As ''DLX''/''Dll'' are involved in limb development in most of the major phyla, including vertebrates, it has been suggested that ''Dll'' was involved in appendage growth in an early bilaterial ancestor. Six members of the family are found in human and mice, numbered DLX1 to DLX6. They form two-gene

cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Cluster II (spacecraft), a European Space Agency mission to study the magnetosphere * Asteroid cluster, a small ...

s (bigene clusters) with each other. There are

DLX1 Homeobox protein DLX-1 is a protein that in humans is encoded by the ''DLX1'' gene. Function This gene encodes a member of a homeobox transcription factor gene family similar to the ''Drosophila'' distal-less gene. The encoded protein is loca ...

DLX2 Homeobox protein DLX-2 is a protein that in humans is encoded by the ''DLX2'' gene. Many vertebrate homeo box-containing genes have been identified on the basis of their sequence similarity with Drosophila developmental genes. Members of the Dlx ...

, DLX3- DLX4,

DLX5 Homeobox protein DLX-5 is a protein that in humans is encoded by the distal-less homeobox 5 gene, or ''DLX5'' gene. DLX5 is a member of the DLX gene family. Function This gene encodes a member of a homeobox transcription factor gene family si ...

DLX6 Homeobox protein DLX-6 is a protein that in humans is encoded by the ''DLX6'' gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is tr ...

clusters in vertebrates, linked to

Hox gene Hox genes, a subset of homeobox, homeobox genes, are a gene cluster, group of related genes that Evolutionary developmental biology, specify regions of the body plan of an embryo along the craniocaudal axis, head-tail axis of animals. Hox protein ...

clusters HOXD, HOXB, and HOXA respectively. In higher fishes like the

zebrafish The zebrafish (''Danio rerio'') is a species of freshwater ray-finned fish belonging to the family Danionidae of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish, frequently sold under the trade name zebra danio (an ...

, there are two additional ''DLX'' genes, ''dlx2b'' (''dlx5'') and ''dlx4a'' (''dlx8''). These additional genes are not linked with each other, or any other ''DLX'' gene. All six other genes remain in bigene clusters. '' DLX4, DLX7, DLX8'' and ''DLX9'' are the same gene in vertebrates. They are named differently because every time the same gene was found, the researchers thought they had found a new gene.

Function

''DLX'' genes, like ''distal-less'', are involved in limb development in most of the major phyla. ''DLX'' genes are involved in craniofacial morphogenesis and the tangential migration of

interneuron Interneurons (also called internuncial neurons, association neurons, connector neurons, or intermediate neurons) are neurons that are not specifically motor neurons or sensory neurons. Interneurons are the central nodes of neural circuits, enab ...

s from the subpallium to the

pallium The pallium (derived from the Roman ''pallium'' or ''palla'', a woolen cloak; : pallia) is an ecclesiastical vestment in the Catholic Church, originally peculiar to the pope, but for many centuries bestowed by the Holy See upon metropolitan bish ...

during vertebrate

brain development The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special sens ...

. It has been suggested that ''DLX'' promotes the migration of

s by repressing a set of proteins that are normally expressed in terminally differentiated neurons and act to promote the outgrowth of

dendrite A dendrite (from Ancient Greek language, Greek δένδρον ''déndron'', "tree") or dendron is a branched cytoplasmic process that extends from a nerve cell that propagates the neurotransmission, electrochemical stimulation received from oth ...

s and

axon An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...

s. Mice lacking DLX1 exhibit electrophysiological and histological evidence consistent with delayed-onset

epilepsy Epilepsy is a group of Non-communicable disease, non-communicable Neurological disorder, neurological disorders characterized by a tendency for recurrent, unprovoked Seizure, seizures. A seizure is a sudden burst of abnormal electrical activit ...

. DLX2 has been associated with a number of areas including development of the zona limitans intrathalamica and the prethalamus. DLX4 (DLX7) is expressed in

bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...

. ''DLX5'' and ''DLX6'' genes are necessary for normal formation of the mandible in vertebrates.

References

{{genarch Gene families Transcription factors