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.

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.

Background/Aims: The short stature homeobox-containing (SHOX) gene is one of many genes that regulate longitudinal growth. The SHOX deficiency (SHOX-D) phenotype, caused by intragenic or regulatory region defects, ranges from normal stature to mesomelic skeletal dysplasia. We investigated differences in radiological anomalies between patients with SHOX-D and Turner syndrome (TS) and the effect of 2 years of growth hormone (GH) treatment on these anomalies. Methods: Left hand/wrist, forearm and lower leg radiographs were assessed at baseline and after 2 years in children with genetically confirmed SHOX-D (GH-treated and untreated groups) and TS (GH-treated) in a randomised, controlled, multinational study. Results: Radiological anomalies of hand, wrist and forearm were common in SHOX-D and TS. Radial bowing appeared more prevalent in SHOX-D, while lower leg anomalies were more common in TS. There were no significant differences in radiological findings between GH-treated and untreated patients with SHOX-D after 2 years. Conclusion: GH treatment had no systematic effect on skeletal findings in SHOX-D, based on limited radiological differences between the GH-treated and untreated groups at 2 years. Bone age radiographs allow assessment of radiological signs indicating a potential diagnosis of SHOX-D and may lead to earlier genetic confirmation and initiation of GH therapy.

Background/Aims: The short stature homeobox-containing (SHOX) gene is one of many genes that regulate longitudinal growth. The SHOX deficiency (SHOX-D) phenotype, caused by intragenic or regulatory region defects, ranges from normal stature to mesomelic skeletal dysplasia. We investigated differences in radiological anomalies between patients with SHOX-D and Turner syndrome (TS) and the effect of 2 years of growth hormone (GH) treatment on these anomalies. Methods: Left hand/wrist, forearm and lower leg radiographs were assessed at baseline and after 2 years in children with genetically confirmed SHOX-D (GH-treated and untreated groups) and TS (GH-treated) in a randomised, controlled, multinational study. Results: Radiological anomalies of hand, wrist and forearm were common in SHOX-D and TS. Radial bowing appeared more prevalent in SHOX-D, while lower leg anomalies were more common in TS. There were no significant differences in radiological findings between GH-treated and untreated patients with SHOX-D after 2 years. Conclusion: GH treatment had no systematic effect on skeletal findings in SHOX-D, based on limited radiological differences between the GH-treated and untreated groups at 2 years. Bone age radiographs allow assessment of radiological signs indicating a potential diagnosis of SHOX-D and may lead to earlier genetic confirmation and initiation of GH therapy.