Monocarboxylate transporter 8

Monocarboxylate transporter 8 (MCT8) is an active transporter protein that in humans is encoded by the SLC16A2 gene.^[5][6][7][8]

SLC16A2
Identifiers
Aliases	SLC16A2, DXS128, DXS128E, MCT 7, MCT 8, MCT7, MCT8, MRX22, XPCT, AHDS, solute carrier family 16 member 2
External IDs	OMIM: 300095; MGI: 1203732; HomoloGene: 39495; GeneCards: SLC16A2; OMA:SLC16A2 - orthologs
Gene location (Human) Chr. X chromosome (human)[1] Band Xq13.2 Start 74,421,493 bp[1] End 74,533,917 bp[1]
Gene location (Mouse) Chr. X chromosome (mouse)[2] Band X D|X 46.29 cM Start 102,741,020 bp[2] End 102,865,589 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right adrenal gland right adrenal cortex right lobe of liver left adrenal gland left adrenal cortex ganglionic eminence ventricular zone anterior pituitary stromal cell of endometrium gallbladder Top expressed in choroid plexus of fourth ventricle Epithelium of choroid plexus left lobe of liver right kidney tail of embryo ligament human kidney internal carotid artery proximal tubule genital tubercle More reference expression data BioGPS More reference expression data
Gene ontology Molecular function symporter activity monocarboxylic acid transmembrane transporter activity transporter activity thyroid hormone transmembrane transporter activity Cellular component integral component of membrane integral component of plasma membrane membrane plasma membrane Biological process monocarboxylic acid transport thyroid hormone transport transmembrane transport sodium-independent organic anion transport Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 6567 20502 Ensembl ENSG00000147100 ENSMUSG00000033965 UniProt P36021 O70324 RefSeq (mRNA) NM_006517 NM_009197 RefSeq (protein) NP_006508 NP_006508.2 NP_033223 Location (UCSC) Chr X: 74.42 – 74.53 Mb Chr X: 102.74 – 102.87 Mb PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Function

MCT8 actively transports a variety of iodo-thyronines including the thyroid hormones T₃ and T₄.^[6]

Clinical significance

A genetic disorder (discovered in 2003^[6] and 2004^[9]) is caused by mutation in the transporter of thyroid hormone, MCT8, also known as SLC16A2, is believed to be account for a significant fraction of the undiagnosed neurological disorders (usually resulting in hypotonic/floppy infants with delayed milestones). This genetic defect was known as Allan–Herndon–Dudley syndrome (since 1944) without knowing its actual cause. It has been shown mutated in cases of X-linked leukoencephalopathy.^[10] Some of the symptoms for this disorder as are follows: normal to slightly elevated TSH, elevated T₃ and reduced T₄ (ratio of T₃/T₄ is about double its normal value). Normal looking at birth and for the first few years, hypotonic (floppy), in particular difficulty to hold the head, possibly difficulty to thrive, possibly with delayed myelination (if so, some cases are reported with an MRI pattern similar to Pelizaeus–Merzbacher disease, known as PMD^[11]), possibly with decreased mitochondrial enzyme activities, possibly with fluctuating lactate level. Patients have an alert face, a limited IQ, patients may never talk/walk, 50% need feeding tube, patients have a normal life span. This disease can be ruled out with a simple TSH/T₄/T₃ thyroid test.

Model organisms

Zebrafish

A knockout zebrafish line was generated in 2014 using the zinc-finger nuclease (ZFN)-mediated targeted gene editing system.^[12] Similar to human patients, the zebrafish larvae exhibited neurological and behavioral deficiencies. They demonstrated reduced locomotor activity, altered myelin-related genes and neuron-specific deficiencies in circuit formation.^[13]

Xenopus

Expression of mct8 has been characterised in Xenopus laevis^[14] and Xenopus tropicalis.^[15]

See also

• Solute carrier family