The monocarboxylate transporter 8 linked to human psychomotor retardation is highly expressed in thyroid hormone-sensitive neuron populations.
Recent genetic analysis in several patients presenting a severe form of X-linked psychomotor retardation combined with abnormal thyroid hormone (TH) levels have revealed mutations or deletions in the gene of the monocarboxylate transporter 8 (MCT8). Because in vitro MCT8 functions as a TH transporter, the complex clinical picture of these patients indicated an important role for MCT8 in TH-dependent processes of brain development. To provide a clue to the cellular function of MCT8 in brain, we studied the expression of MCT8 mRNA in the murine central nervous system by in situ hybridization histochemistry. In addition to the choroid plexus structures, the highest transcript levels were found in neo- and allocortical regions (e.g. olfactory bulb, cerebral cortex, hippocampus, and amygdala), moderate signal intensities in striatum and cerebellum, and low levels in a few neuroendocrine nuclei. Colocalization studies revealed that MCT8 is predominantly expressed in neurons. Together with the spatiotemporal expression pattern of MCT8 during the perinatal period, these results strongly indicate that MCT8 plays an important role for proper central nervous system development by transporting TH into neurons as its main target cells.
Heuer
Heike
H
Institute of Molecular Biotechnology, Beutenbergstrasse 11, D-07745 Jena, Germany. hheuer@imb-jena.de
Maier
Michael K
MK
Iden
Sandra
S
Mittag
Jens
J
Friesema
Edith C H
EC
Visser
Theo J
TJ
Bauer
Karl
K
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics*; D005260:Female; D006801:Humans; D007453:Iodide Peroxidase / Q000235:genetics; D008297:Male; D051379:Mice; D027501:Monocarboxylic Acid Transporters / Q000235:genetics* / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000235:genetics; D011596:Psychomotor Disorders / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D027981:Symporters; D013963:Thyroid Hormones / Q000378:metabolism*; D000097564:Iodothyronine Deiodinase Type II
D002352:Carrier Proteins; D007453:Iodide Peroxidase; D027501:Monocarboxylic Acid Transporters; D027701:Organic Cation Transport Proteins; D012333:RNA, Messenger; D027981:Symporters; D013963:Thyroid Hormones; D000097564:Iodothyronine Deiodinase Type II; C464433:Oatp2 protein, mouse; C090735:SLC16A2 protein, human