Identification of Transient Receptor Potential Channel 4-Associated Protein as a Novel Candidate Gene Causing Congenital Primary Hypothyroidism.
BACKGROUND
Congenital primary hypothyroidism (CH) is the most common endocrine disorder in neonates.


METHODS
To identify novel genes, we performed whole exome sequencing (WES) in 6 patients with CH due to thyroid dysgenesis (TD). The potential effects of the most relevant variants were analyzed using in silico prediction tools. The most promising candidate gene, transient receptor potential channel 4-associated protein (TRPC4AP), was sequenced in 179 further patients with TD. Expression of TRPC4AP in human thyroid was investigated using RT-PCR. Trpc4ap- functional analysis was performed in Xenopus laevis using Morpholino (MO) antisense oligomers.


RESULTS
WES identified a likely damaging mutation in TRPC4AP leading to a de novo stop codon p.Q552*. Targeted sequencing of TRPC4AP demonstrated gene variants with predicted damaging potential in 5 patients resulting each in an amino acid exchange (p.P706S, p.F729L, p.S777C, and p.N229S). We demonstrated that TRPC4AP is expressed in human thyroid gland tissue. Using Xenopus laevis, we showed that the volume of the tadpole thyroid anlage was reduced by 20% in Trpc4ap MO knockdowns compared to controls and by 41% in "Clustered Regularly Interspaced Short Palindromic Repeats"/Cas9-mediated gene knockout experiments.


DISCUSSION
A recognized interaction of TRPC4AP and the NF-kappa-B-essential-modulator encoded by IKBKG gene was identified by IPA analysis. IKBKG plays a role in activation of the NF-κB-signaling pathway and regulates genes involved in proliferation and survival of thyrocytes and expression of key enzymes of thyroid hormone synthesis.


CONCLUSION
TRPC4AP was identified as a novel candidate gene in TD, but further studies are needed to validate its role in thyroid function.
['Choukair|Daniela|D|', 'Eberle|Birgit|B|', 'Vick|Philipp|P|', 'Hermanns|Pia|P|', 'Weiss|Birgit|B|', 'Paramasivam|Nagarajan|N|', 'Schlesner|Matthias|M|', 'Lornsen|Katharina|K|', 'Roeth|Ralph|R|', 'Klutmann|Carina|C|', 'Kreis|Jennifer|J|', 'Hoffmann|Georg F|GF|', 'Pohlenz|Joachim|J|', 'Rappold|Gudrun A|GA|', 'Bettendorf|Markus|M|']
D000293:Adolescent D002648:Child D002675:Child, Preschool D003409:Congenital Hypothyroidism D004252:DNA Mutational Analysis D005260:Female D020022:Genetic Predisposition to Disease D006801:Humans D051550:I-kappa B Kinase D008297:Male D009154:Mutation D016328:NF-kappa B D050052:TRPC Cation Channels D050033:Thyroid Dysgenesis D000073359:Whole Exome Sequencing
Congenital primary hypothyroidism Thyroid dysgenesis Whole exome screening