Clinical phenotype and genetic function analysis of a family with hypomyelinating leukodystrophy-7 caused by POLR3A mutation.

Hypomyelinating leukodystrophy (HLD) is a rare genetic heterogeneous disease that can affect myelin development in the central nervous system. This study aims to analyze the clinical phenotype and genetic function of a family with HLD-7 caused by POLR3A mutation. The proband (IV6) in this family mainly showed progressive cognitive decline, dentin dysplasia, and hypogonadotropic hypogonadism. Her three old brothers (IV1, IV2, and IV4) also had different degrees of ataxia, dystonia, or dysarthria besides the aforementioned manifestations. Their brain magnetic resonance imaging showed bilateral periventricular white matter atrophy, brain atrophy, and corpus callosum atrophy and thinning. The proband and her two living brothers (IV2 and IV4) were detected to carry a homozygous mutation of the POLR3A (NM_007055.4) gene c. 2300G > T (p.Cys767Phe), and her consanguineous married parents (III1 and III2) were p.Cys767Phe heterozygous carriers. In the constructed POLR3A wild-type and p.Cys767Phe mutant cells, it was seen that overexpression of wild-type POLR3A protein significantly enhanced Pol III transcription of 5S rRNA and tRNA Leu-CAA. However, although the mutant POLR3A protein overexpression was increased compared to the wild-type protein overexpression, it did not show the expected further enhancement of Pol III function. On the contrary, Pol III transcription function was frustrated (POLR3A, BC200, and tRNA Leu-CAA expression decreased), and MBP and 18S rRNA expressions were decreased. This study indicates that the POLR3A p.Cys767Phe variant caused increased expression of mutated POLR3A protein and abnormal expression of Pol III transcripts, and the mutant POLR3A protein function was abnormal.

Evaluation of ferritin and TfR level in plasma neural-derived exosomes as potential markers of Parkinson's disease.

Introduction: Early diagnosis of Parkinson's disease (PD) remains challenging. It has been suggested that abnormal brain iron metabolism leads to excessive iron accumulation in PD, although the mechanism of iron deposition is not yet fully understood. Ferritin and transferrin receptor (TfR) are involved in iron metabolism, and the exosome pathway is one mechanism by which ferritin is transported and regulated. While the blood of healthy animals contains a plentiful supply of TfR-positive exosomes, no studies have examined ferritin and TfR in plasma neural-derived exosomes. Methods: Plasma exosomes were obtained from 43 patients with PD and 34 healthy controls. Neural-derived exosomes were isolated with anti-human L1CAM antibody immunoabsorption. Transmission electron microscopy and western blotting were used to identify the exosomes. ELISAs were used to quantify ferritin and TfR levels in plasma neural-derived exosomes of patients with PD and controls. Receivers operating characteristic (ROC) curves were applied to map the diagnostic accuracy of ferritin and TfR. Independent predictors of the disease were identified using logistic regression models. Results: Neural-derived exosomes exhibited the typical exosomal morphology and expressed the specific exosome marker CD63. Ferritin and TfR levels in plasma neural-derived exosomes were significantly higher in patients with PD than controls (406.46 ± 241.86 vs. 245.62 ± 165.47 ng/µg, P = 0.001 and 1728.94 ± 766.71 vs. 1153.92 ± 539.30 ng/µg, P < 0.001, respectively). There were significant positive correlations between ferritin and TfR levels in plasma neural-derived exosomes in control group, PD group and all the individuals (rs = 0.744, 0.700, and 0.752, respectively). The level of TfR was independently associated with the disease (adjusted odds ratio 1.002; 95% CI 1.000-1.003). ROC performances of ferritin, TfR, and their combination were moderate (0.730, 0.812, and 0.808, respectively). However, no relationship was found between the biomarkers and disease progression. Conclusion: It is hypothesized that ferritin and TfR in plasma neural-derived exosomes may be potential biomarkers for PD, and that they may participate in the mechanism of excessive iron deposition in PD.

Han family with essential tremor caused by the P421L variant of the TENM4 gene in China.

BACKGROUND: Essential tremor (ET) is an autosomal dominant inheritance disorder. Mutations in fusion sarcoma (FUS), mitochondrial serine peptidase 2 (HTRA2), teneurin transmembrane protein 4 (TENM4), sortilin1 (SORT1), SCN11A, and notch2N-terminal-like (NOTCH2NLC) genes are associated with familial ET. METHODS: A proband with ET was tested using whole-exome sequencing and repeat-primed polymerase chain reaction. Subsequently, the family members were screened for the suspected mutation, and the results were verified using Sanger sequencing. The relationship between pedigree and phenotype was also analyzed, and structural and functional changes in the variants were predicted using bioinformatics analysis. RESULTS: In a family with ET, the proband (III4) and the proband's father (II1), grandfather (I1), uncle (II2), and cousin (III5) all presented with involuntary tremors of both upper limbs. The responsible mutation was identified as TENM4 c.1262C > T (p.P421L), which showed genetic co-segregation in the family survey. AlphaFold predicted a change in the spatial position of TENM4 after the P421L mutation, which may have affected its stability. AlphaFold also predicted P421L to be a deleterious variation, which would lead to lower degrees of freedom of the TENM4 protein, thereby affecting the protein's structure and stability. According to the bioinformatics analysis, TENM4 (p.P421L) may reduce the signal reaching the nucleus by affecting the expression of TENM4 messenger RNA (mRNA), thereby impairing the normal oligodendrocyte differentiation process and leading to impaired myelination. CONCLUSION: This study revealed that the TENM4 (p.P421L) pathogenic missense variation was responsible for ET in the proband.

Corrigendum: Evaluation of ferritin and TfR level in plasma neural-derived exosomes as potential markers of Parkinson's disease.

[This corrects the article DOI: 10.3389/fnagi.2023.1216905.].

Differences in gut microbiota structure in patients with stages 4-5 chronic kidney disease.

The gut microbiota can affect human metabolism, immunity, and other biologic pathways through the complex gut-kidney axis (GKA), and in turn participate in the occurrence and development of kidney disease. In this study, 39 patients with stage 4-5 chronic kidney disease (CKD) and 40 healthy individuals were recruited and 16S rDNA sequencing was performed to analyze the V3-V4 conserved regions of their microbiota. A total of 795 operational taxonomic units (OTUs) shared between groups or specific to each group were obtained, among which 255 OTUs with significant differences between the two groups were identified (P<0.05). Adonis differential analysis showed that the diversity of gut microbiota was highly correlated with CKD stages 4-5. Additionally, 61 genera with differences in the two groups were identified (P<0.05) and 111 species with significant differences in the phyla, classes, orders, families, and genera between the two groups were identified (P<0.05). The differential bacterial genera with the greatest contribution were, in descending order: c_Bacteroidia, o_Bacteroidales, p_Bacteroidetes, c_Clostridia, o_Clostridiales, etc. Those with the greatest contribution in stages 4-5 CKD were, in descending order: p_Proteobacteria, f_Enterobacteriaceae, o_Enterobacteriales, c_Gammaproteobacteria, c_Bacilli, etc. The results suggest that the diversity of the microbiota may affect the occurrence, development, and outcome of the terminal stages of CKD.

Review and Analysis of Two Gitelman Syndrome Pedigrees Complicated with Proteinuria or Hashimoto's Thyroiditis Caused by Compound Heterozygous SLC12A3 Mutations.

Gitelman syndrome (GS) is an autosomal recessive inherited salt-losing renal tubular disease, which is caused by a pathogenic mutation of SLC12A3 encoding thiazide-sensitive Na-Cl cotransporter, which leads to disturbance of sodium and chlorine reabsorption in renal distal convoluted tubules, resulting in phenotypes such as hypovolemia, renin angiotensin aldosterone system (RAAS) activation, hypokalemia, and metabolic alkalosis. In this study, two GS families with proteinuria or Hashimoto's thyroiditis were analyzed for genetic-phenotypic association. Sanger sequencing revealed that two probands carried SLC12A3 compound heterozygous mutations, and proband A carried two pathogenic mutations: missense mutation Arg83Gln, splicing mutation, or frameshift mutation NC_000016.10:g.56872655_56872667 (gcggacatttttg>accgaaaatttt) in exon 8. Proband B carries two missense mutations: novel Asp839Val and Arg904Gln. Both probands manifested hypokalemia, hypomagnesemia, hypocalcinuria, metabolic alkalosis, and RAAS activation; in addition, the proband A exhibited decreased urinary chloride, phosphorus, and increased magnesium ions excretion, complicated with Hashimoto's Thyroiditis, while the proband B exhibited enhanced urine sodium excretion and proteinuria. The older sister of proband B with GS also had Hashimoto's thyroiditis. Electron microscopy revealed swelling and vacuolar degeneration of glomerular epithelial cells, diffuse proliferation of mesangial cells and matrix, accompanied by a small amount of low-density electron-dense deposition, and segmental fusion of epithelial cell foot processes in proband B. Light microscopy showed mild mesangial hyperplasia in the focal segment of the glomerulus, hyperplasia, and hypertrophy of juxtaglomerular apparatus cells, mild renal tubulointerstitial lesions, and one glomerular sclerosis. So, long-term hypokalemia of GS can cause kidney damage and may also be susceptible to thyroid disease.