GFR measurements and ultrasound findings in 154 children with a congenital solitary functioning kidney.

BACKGROUND: Multicystic dysplastic kidney (MCDK) and unilateral renal agenesis (URA) are the most common reasons for a congenital solitary functioning kidney (SFK). We aimed to assess the presence of abnormalities in the congenital SFK and evaluate kidney function using chrome EDTA (CrEDTA) measurements. METHODS: We retrospectively reviewed the medical records of 154 children with MCDK and URA in the period from 2005 to 2022 to analyze results from ultrasound scans and CrEDTA glomerular filtration rate (GFR) examinations. RESULTS: Of 154 children with a solitary kidney due to MCDK (62%) or URA (38%), abnormalities on the congenital SFK were found in 13 children (8%). The abnormalities spontaneously resolved in 6 children (46%). The most common abnormality was hydronephrosis. Compensatory hypertrophy was found in 17% of the children within the first 6 months of life. 116 children (90%) had a standard GFR (sdGFR) above 75% of expected for the age. Out of those with a sdGFR below 75% of expected, 3 (23%) had abnormalities in the congenital SFK. There was no difference in sdGFR between children with MCDK and URA. CONCLUSIONS: Our study is the first using CrEDTA for GFR measurements and suggests that most children with a congenital SFK due to MCDK or URA have a kidney function within expected for the age. Compensatory hypertrophy of the SFK is found in a minority of children within the first six months of life, suggesting that this process is developing over time. The prevalence of abnormalities in the SFK seems low, however those with abnormalities (e.g. hydronephrosis) are at higher risk of reduced sdGFR.

The Novel Ser18del AVP Variant Causes Inherited Neurohypophyseal Diabetes Insipidus by Mechanisms Shared with Other Signal Peptide Variants.

BACKGROUND/AIM: Variability in the severity and age at onset of autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI) may be associated with certain types of variants in the arginine vasopressin (AVP) gene. In this study, we aimed to describe a large family with an apparent predominant female occurrence of polyuria and polydipsia and to determine the underlying cause. METHODS: The family members reported their family demography and symptoms. Two subjects were diagnosed by fluid deprivation and dDAVP challenge tests. Eight subjects were tested genetically. The identified variant along with 3 previously identified variants in the AVP gene were investigated by heterologous expression in a human neuronal cell line (SH-SY5Y). RESULTS: Both subjects investigated clinically had a partial neurohypophyseal diabetes insipidus phenotype. A g.276_278delTCC variant in the AVP gene causing a Ser18del deletion in the signal peptide (SP) of the AVP preprohormone was perfectly co-segregating with the disease. When expressed in SH-SY5Y cells, the Ser18del variant along with 3 other SP variants (g.227G>A, Ser17Phe, and Ala19Thr) resulted in reduced AVP mRNA, impaired AVP secretion, and partial AVP prohormone degradation and retention in the endoplasmic reticulum. Impaired SP cleavage was demonstrated directly in cells expressing the Ser18del, g.227G>A, and Ala19Thr variants, using state-of-the-art mass spectrometry. CONCLUSION: Variants affecting the SP of the AVP preprohormone cause adFNDI with variable phenotypes by a mechanism that may involve impaired SP cleavage combined with effects at the mRNA, protein, and cellular level.

Induced pluripotent stem cells derived from a patient with autosomal dominant familial neurohypophyseal diabetes insipidus caused by a variant in the AVP gene.

Autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI) is caused by variants in the arginine vasopressin (AVP) gene. Here we report the generation of induced pluripotent stem cells (iPSCs) from a 42-year-old man carrying an adFNDI causing variant in exon 1 of the AVP gene using lentivirus-mediated nuclear reprogramming. The iPSCs carried the expected variant in the AVP gene. Furthermore, the iPSCs expressed pluripotency markers; displayed in vitro differentiation potential to the three germ layers and had a normal karyotype consistent with the original fibroblasts. This iPSC line is useful in future studies focusing on the pathogenesis of adFNDI.