Differences in the urinary metabolome and proteome between wet and dry nights in children with monosymptomatic nocturnal enuresis and nocturnal polyuria.

BACKGROUND: Nocturnal enuresis (NE) is a common disease with multiple pathogenic mechanisms. This study aimed to compare levels of metabolites and proteins between wet and dry nights in urine samples from children with monosymptomatic NE (MNE). METHODS: Ten boys with MNE and nocturnal polyuria (age: 7.6 ± 1.3 years) collected their total nighttime urine production during a wet and a dry night. Untargeted metabolomics and proteomics were performed on the urine samples by liquid chromatography coupled with high-mass accuracy tandem mass spectrometry (LC-MS/MS). RESULTS: On wet nights, we found reduced urine osmolality (P = 0.025) and increased excretion of urinary potassium and sodium by a factor of, respectively, 2.1 (P = 0.038) and 1.9 (P = 0.19) compared with dry nights. LC-MS identified 59 metabolites and 84 proteins with significantly different levels between wet and dry nights (fold change (FC) < 0.67 or > 1.5, P < 0.05). Some compounds were validated by different methodologies. During wet nights, levels of compounds related to oxidative stress and blood pressure, including adrenalin, were increased. We found reduced levels of aquaporin-2 on wet nights. The FCs in the 59 metabolites were positively correlated to the FCs in the same metabolites identified in urine samples obtained during the evening preceding wet and dry nights. CONCLUSIONS: Oxidative stress, which in the literature has been associated with nocturia and disturbances in sleep, might be increased during wet nights in children with MNE. We further found evidence of increased sympathetic activity. The mechanisms related to having wet nights in children with MNE seem complex, and both free water and solute handling appear to be important. A higher resolution version of the Graphical abstract is available as Supplementary information.

New insights in the genetic variant spectrum of SLC34A2 in pulmonary alveolar microlithiasis; a systematic review.

Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive lung disease caused by variants in the SLC34A2 gene encoding the sodium-dependent phosphate transport protein 2B, NaPi-2b. PAM is characterized by deposition of calcium phosphate crystals in the alveoli. Onset and clinical course vary considerably; some patients remain asymptomatic while others develop severe respiratory failure with a significant symptom burden and compromised survival. It is likely that PAM is under-reported due to lack of recognition, misdiagnosis, and mild clinical presentation. Most patients are genetically uncharacterized as the diagnostic confirmation of PAM has traditionally not included a genetic analysis. Genetic testing may in the future be the preferred tool for diagnostics instead of invasive methods. This systematic review aims to provide an overview of the growing knowledge of PAM genetics. Rare variants in SLC34A2 are found in almost all genetically tested patients. So far, 34 allelic variants have been identified in at least 68 patients. A majority of these are present in the homozygous state; however, a few are found in the compound heterozygous form. Most of the allelic variants involve only a single nucleotide. Half of the variants are either nonsense or frameshifts, resulting in premature termination of the protein or decay of the mRNA. There is currently no cure for PAM, and the only effective treatment is lung transplantation. Management is mainly symptomatic, but an improved understanding of the underlying pathophysiology will hopefully result in development of targeted treatment options. More standardized data on PAM patients, including a genetic diagnosis covering larger international populations, would support the design and implementation of clinical studies to the benefit of patients. Further genetic characterization and understanding of how the molecular changes influence disease phenotype will hopefully allow earlier diagnosis and treatment of the disease in the future.

The genetics of incontinence: A scoping review.

The genetic causes underlying incontinence in both children and adults have begun to be unravelled during the last decades. The aim of this scoping review is to synthesize current knowledge on the genetics of childhood and adult urinary and faecal incontinence, identify similarities between different incontinence subgroups, and identify knowledge gaps to aid future research. PRISMA-ScR was used, and 76 studies were included. Early epidemiological family and twin studies suggest high heritability of incontinence. Linkage studies provide evidence for the existence of rare genetic variants; however, these variants have not been identified. Later candidate gene association studies and recent genome-wide association studies provide the first preliminary evidence that common risk variants also play a role. The genetics of incontinence in children and adults has predominantly been studied separately, but this review identifies for the first time the endothelin system as a potential common pathophysiological pathway. Overall, these findings strengthen the hypothesis that genetic variants play a prominent role in the pathogenesis of incontinence. Future research should include hypothesis-free studies of rare and common variants in large well-characterized cohorts with incontinence. Studies should include different age groups and ethnicities and both sexes to fully reveal the genetics of incontinence.

The psychiatric risk gene BRD1 modulates mitochondrial bioenergetics by transcriptional regulation.

Bromodomain containing 1 (BRD1) encodes an epigenetic regulator that controls the expression of genetic networks linked to mental illness. BRD1 is essential for normal brain development and its role in psychopathology has been demonstrated in genetic and preclinical studies. However, the neurobiology that bridges its molecular and neuropathological effects remains poorly explored. Here, using publicly available datasets, we find that BRD1 targets nuclear genes encoding mitochondrial proteins in cell lines and that modulation of BRD1 expression, irrespective of whether it is downregulation or upregulation of one or the other existing BRD1 isoforms (BRD1-L and BRD1-S), leads to distinct shifts in the expression profile of these genes. We further show that the expression of nuclear genes encoding mitochondrial proteins is negatively correlated with the expression of BRD1 mRNA during human brain development. In accordance, we identify the key gate-keeper of mitochondrial metabolism, Peroxisome proliferator-activated receptor (PPAR) among BRD1's co-transcription factors and provide evidence that BRD1 acts as a co-repressor of PPAR-mediated transcription. Lastly, when using quantitative PCR, mitochondria-targeted fluorescent probes, and the Seahorse XFe96 Analyzer, we demonstrate that modulation of BRD1 expression in cell lines alters mitochondrial physiology (mtDNA content and mitochondrial mass), metabolism (reducing power), and bioenergetics (among others, basal, maximal, and spare respiration) in an expression level- and isoform-dependent manner. Collectively, our data suggest that BRD1 is a transcriptional regulator of nuclear-encoded mitochondrial proteins and that disruption of BRD1's genomic actions alters mitochondrial functions. This may be the mechanism underlying the cellular and atrophic changes of neurons previously associated with BRD1 deficiency and suggests that mitochondrial dysfunction may be a possible link between genetic variation in BRD1 and psychopathology in humans.

Impaired phosphate transport in SLC34A2 variants in patients with pulmonary alveolar microlithiasis.

BACKGROUND: Variants in SLC34A2 encoding the sodium-dependent phosphate transport protein 2b (NaPi-IIb) cause the rare lung disease pulmonary alveolar microlithiasis (PAM). PAM is characterised by the deposition of calcium-phosphate concretions in the alveoli usually progressing over time. No effective treatment is available. So far, 30 allelic variants in patients have been reported but only a few have been functionally characterised. This study aimed to determine the impact of selected SLC34A2 variants on transporter expression and phosphate uptake in cellular studies. METHODS: Two nonsense variants (c.910A > T and c.1456C > T), one frameshift (c.1328delT), and one in-frame deletion (c.1402_1404delACC) previously reported in patients with PAM were selected for investigation. Wild-type and mutant c-Myc-tagged human NaPi-IIb constructs were expressed in Xenopus laevis oocytes. The transport function was investigated with a 32Pi uptake assay. NaPi-IIb protein expression and localisation were determined with immunoblotting and immunohistochemistry, respectively. RESULTS: Oocytes injected with the wild-type human NaPi-IIb construct had significant 32Pi transport compared to water-injected oocytes. In addition, the protein had a molecular weight as expected for the glycosylated form, and it was readily detectable in the oocyte membrane. Although the protein from the Thr468del construct was synthesised and expressed in the oocyte membrane, phosphate transport was similar to non-injected control oocytes. All other mutants were non-functional and not expressed in the membrane, consistent with the expected impact of the truncations caused by premature stop codons. CONCLUSIONS: Of four analysed SLC34A2 variants, only the Thr468del showed similar protein expression as the wild-type cotransporter in the oocyte membrane. All mutant transporters were non-functional, supporting that dysfunction of NaPi-IIb underlies the pathology of PAM.

Inactivation of the Schizophrenia-associated BRD1 gene in Brain Causes Failure-to-thrive, Seizure Susceptibility and Abnormal Histone H3 Acetylation and N-tail Clipping.

Genetic studies have repeatedly shown that the Bromodomain containing 1 gene, BRD1, is involved in determining mental health, and the importance of the BRD1 protein for normal brain function has been studied in both cell models and constitutive haploinsufficient Brd1+/- mice. Homozygosity for inactivated Brd1 alleles is lethal during embryonic development in mice. In order to further characterize the molecular functions of BRD1 in the brain, we have developed a novel Brd1 knockout mouse model (Brd1-/-) with bi-allelic conditional inactivation of Brd1 in the central nervous system. Brd1-/- mice were viable but smaller and with reduced muscle strength. They showed reduced exploratory behavior and increased sensitivity to pentylenetetrazole-induced seizures supporting the previously described GABAergic dysfunction in constitutive Brd1+/- mice. Because BRD1 takes part in protein complexes with histone binding and modifying functions, we investigated the effect of BRD1 depletion on the global histone modification pattern in mouse brain by mass spectrometry. We found decreased levels of histone H3 acetylation (H3K9ac, H3K14ac, and H3K18ac) and increased N-tail clipping in consequence of BRD1 depletion. Collectively, the presented results support that BRD1 controls gene expression at the epigenetic level by regulating histone H3 proteoforms in the brain.

Genome-wide association study implicates CHRNA2 in cannabis use disorder.

Cannabis is the most frequently used illicit psychoactive substance worldwide; around one in ten users become dependent. The risk for cannabis use disorder (CUD) has a strong genetic component, with twin heritability estimates ranging from 51 to 70%. Here we performed a genome-wide association study of CUD in 2,387 cases and 48,985 controls, followed by replication in 5,501 cases and 301,041 controls. We report a genome-wide significant risk locus for CUD (P = 9.31 × 10-12) that replicates in an independent population (Preplication = 3.27 × 10-3, Pmeta-analysis = 9.09 × 10-12). The index variant (rs56372821) is a strong expression quantitative trait locus for cholinergic receptor nicotinic α2 subunit (CHRNA2); analyses of the genetically regulated gene expression identified a significant association of CHRNA2 expression with CUD in brain tissue. At the polygenic level, analyses revealed a significant decrease in the risk of CUD with increased load of variants associated with cognitive performance. The results provide biological insights and inform on the genetic architecture of CUD.

Brain proteome changes in female Brd1+/- mice unmask dendritic spine pathology and show enrichment for schizophrenia risk.

Genetic and molecular studies have implicated the Bromodomain containing 1 (BRD1) gene in the pathogenesis of schizophrenia and bipolar disorder. Accordingly, mice heterozygous for a targeted deletion of Brd1 (Brd1+/- mice) show behavioral phenotypes with broad translational relevance to psychiatric disorders. BRD1 encodes a scaffold protein that affects the expression of many genes through modulation of histone acetylation. BRD1 target genes have been identified in cell lines; however the impact of reduced Brd1 levels on the brain proteome is largely unknown. In this study, we applied label-based quantitative mass spectrometry to profile the frontal cortex, hippocampus and striatum proteome and synaptosomal proteome of female Brd1+/- mice. We successfully quantified between 1537 and 2196 proteins and show widespread changes in protein abundancies and compartmentalization. By integrative analysis of human genetic data, we find that the differentially abundant proteins in frontal cortex and hippocampus are enriched for schizophrenia risk further linking the actions of BRD1 to psychiatric disorders. Affected proteins were further enriched for proteins involved in processes known to influence neuronal and dendritic spine morphology e.g. regulation of cytoskeleton dynamics and mitochondrial function. Directly prompted in these findings, we investigated dendritic spine morphology of pyramidal neurons in anterior cingulate cortex and found them significantly altered, including reduced size of small dendritic spines and decreased number of the mature mushroom type. Collectively, our study describes known as well as new mechanisms related to BRD1 dysfunction and its role in psychiatric disorders, and provides evidence for the molecular and cellular dysfunctions underlying altered neurosignalling and cognition in Brd1+/- mice.

Genome-wide association analyses identify 44 risk variants and refine the genetic architecture of major depression.

Major depressive disorder (MDD) is a common illness accompanied by considerable morbidity, mortality, costs, and heightened risk of suicide. We conducted a genome-wide association meta-analysis based in 135,458 cases and 344,901 controls and identified 44 independent and significant loci. The genetic findings were associated with clinical features of major depression and implicated brain regions exhibiting anatomical differences in cases. Targets of antidepressant medications and genes involved in gene splicing were enriched for smaller association signal. We found important relationships of genetic risk for major depression with educational attainment, body mass, and schizophrenia: lower educational attainment and higher body mass were putatively causal, whereas major depression and schizophrenia reflected a partly shared biological etiology. All humans carry lesser or greater numbers of genetic risk factors for major depression. These findings help refine the basis of major depression and imply that a continuous measure of risk underlies the clinical phenotype.

Novel and recurrent variants in AVPR2 in 19 families with X-linked congenital nephrogenic diabetes insipidus.

Congenital nephrogenic diabetes insipidus (CNDI) is characterized by the reduced ability of renal collecting duct cells to reabsorb water in response to the antidiuretic effect of vasopressin. Chronic polyuria and polydipsia are the hallmarks of the disease. Approximately 90% of all patients with CNDI have X-linked inherited disease caused by variants in the arginine vasopressin receptor 2 (AVPR2) gene. We present genetic findings in 34 individuals from 19 kindreds including one or more family members with CNDI. Coding regions of AVPR2 were sequenced bi-directionally. We identified eight novel disease-causing variants in AVPR2, p.Arg68Alafs*124, p.Ser171Arg, p.Gln174Pro, p.Trp200Arg, p.Gly201Cys, p.Gly220Arg, p.Val226Glu, and p.Gln291Pro in nine kindreds. In all three families with more than one affected individual, the novel variants segregated with the disease. We also identified eight recurrent disease-causing variants, p.Val88Met, p.Leu111Valfs*80, p.Arg113Trp, p.Tyr124*, p.Ser167Leu, p.Thr207Asn, p.Arg247Alafs*12, and p.Arg337* in ten kindreds. Our findings contribute to the growing list of AVPR2 variants causing X-linked CNDI. CONCLUSION: Being a rapid diagnostic tool for CNDI, direct sequencing of AVPR2 should be encouraged in newborns with familial predisposition to CNDI. What is Known: • Disease-causing variants in AVPR2 cause X-linked congenital nephrogenic diabetes insipidus (CNDI). • DNA sequencing of AVPR2 is rapid, facilitates differential diagnosis, early intervention, and genetic diagnosis thus reducing morbidity in CNDI. What is New: • We identified eight novel disease-causing variants in AVPR2: p.Arg68Alafs*124, p.Ser171Arg, p.Gln174Pro, p.Trp200Arg, p.Gly201Cys, p.Gly220Arg, p.Val226Glu, and p.Gln291Pro, thereby adding to the growing list of AVPR2 disease-causing variants and emphasizing the importance of genetic testing in CNDI.

The importance of data structure in statistical analysis of dendritic spine morphology.

BACKGROUND: Dendritic spine morphology is heterogeneous and highly dynamic. To study the changing or aberrant morphology in test setups, often spines from several neurons from a few experimental units e.g. mice or primary neuronal cultures are measured. This strategy results in a multilevel data structure, which, when not properly addressed, has a high risk of producing false positive and false negative findings. METHODS: We used mixed-effects models to deal with data with a multilevel data structure and compared this method to analyses at each level. We apply these statistical tests to a dataset of dendritic spine morphology parameters to illustrate advantages of multilevel mixed-effects model, and disadvantages of other models. RESULTS: We present an application of mixed-effects models for analyzing dendritic spine morphology datasets while correcting for the data structure. COMPARISON WITH EXISTING METHODS: We further show that analyses at spine level and aggregated levels do not adequately account for the data structure, and that they may lead to erroneous results. CONCLUSION: We highlight the importance of data structure in dendritic spine morphology analyses and highly recommend the use of mixed-effects models or other appropriate statistical methods to deal with multilevel datasets. Mixed-effects models are easy to use and superior to commonly used methods by including the data structure and the addition of other explanatory variables, for example sex, and age, etc., as well as interactions between variables or between variables and level identifiers.

Novel de novo AVPR2 Variant in a Patient with Congenital Nephrogenic Diabetes Insipidus.

Early diagnosis and treatment of congenital nephrogenic diabetes insipidus (CNDI) are essential due to the risk of intellectual disability caused by repeated episodes of dehydration and rapid rehydration. Timely genetic testing for disease-causing variants in the arginine vasopressin receptor 2 (AVPR2) gene is possible in at-risk newborns with a known family history of X-linked CNDI. In this study, a Swedish male with no family history was diagnosed with CNDI at 6 months of age during an episode of gastroenteritis. We analyzed the coding regions of AVPR2 by PCR and direct DNA sequencing and identified an 80-bp duplication in exon 2 (GenBank NM_000054.4; c.800_879dup) in the proband. This variant leads to a frameshift and introduces a stop codon four codons downstream (p.Ala294Profs*4). The variant gene product either succumbs to nonsense-mediated decay or is translated to a truncated nonfunctional vasopressin V2 receptor. This variant was absent in four unaffected family members, including his parents, as well as in 100 alleles from healthy controls, and is thus considered a novel de novo disease-causing variant. Identification of the disease-causing variant facilitated precise diagnosis of CNDI in the proband. Furthermore, it allows future genetic counseling in the family. This case study highlights the importance of genetic testing in sporadic infant cases with CNDI that can occur due to de novo variants in AVPR2 or several generations of female transmission of the disease-causing variant.

The Schizophrenia-Associated BRD1 Gene Regulates Behavior, Neurotransmission, and Expression of Schizophrenia Risk Enriched Gene Sets in Mice.

BACKGROUND: The schizophrenia-associated BRD1 gene encodes a transcriptional regulator whose comprehensive chromatin interactome is enriched with schizophrenia risk genes. However, the biology underlying the disease association of BRD1 remains speculative. METHODS: This study assessed the transcriptional drive of a schizophrenia-associated BRD1 risk variant in vitro. Accordingly, to examine the effects of reduced Brd1 expression, we generated a genetically modified Brd1+/- mouse and subjected it to behavioral, electrophysiological, molecular, and integrative genomic analyses with focus on schizophrenia-relevant parameters. RESULTS: Brd1+/- mice displayed cerebral histone H3K14 hypoacetylation and a broad range of behavioral changes with translational relevance to schizophrenia. These behaviors were accompanied by striatal dopamine/serotonin abnormalities and cortical excitation-inhibition imbalances involving loss of parvalbumin immunoreactive interneurons. RNA-sequencing analyses of cortical and striatal micropunches from Brd1+/- and wild-type mice revealed differential expression of genes enriched for schizophrenia risk, including several schizophrenia genome-wide association study risk genes (e.g., calcium channel subunits [Cacna1c and Cacnb2], cholinergic muscarinic receptor 4 [Chrm4)], dopamine receptor D2 [Drd2], and transcription factor 4 [Tcf4]). Integrative analyses further found differentially expressed genes to cluster in functional networks and canonical pathways associated with mental illness and molecular signaling processes (e.g., glutamatergic, monoaminergic, calcium, cyclic adenosine monophosphate [cAMP], dopamine- and cAMP-regulated neuronal phosphoprotein 32 kDa [DARPP-32], and cAMP responsive element binding protein signaling [CREB]). CONCLUSIONS: Our study bridges the gap between genetic association and pathogenic effects and yields novel insights into the unfolding molecular changes in the brain of a new schizophrenia model that incorporates genetic risk at three levels: allelic, chromatin interactomic, and brain transcriptomic.

Quantitative assessment of methyl-esterification and other side reactions in a standard propionylation protocol for detection of histone modifications.

Histone modifications play an important role in regulating chromatin stability and gene expression, but to date, investigating them remains challenging. In order to obtain peptides suitable for MS-based analysis, chemical derivatization of N-terminus and lysine residues by propionic anhydride is commonly performed. Several side reactions (methyl-esterification, amidation, solvolysis, overpropionylation, and missed propionylation) during propionylation protocols have been described, yet their relative abundances remain vague. Because methyl-esterification could interfere with correct interpretation of the modification pattern, it is essential to take measures to avoid it. Here we present in-depth quantitative analyses of methyl-esterification and the other side reactions in a standard propionylation protocol containing methanol, and when replacing methanol with isopropanol or acetonitrile. We show that the use of alternative solvents can eliminate methyl-esterification and that even though other side reactions are not prevented, their contribution can be kept relatively small. We also show that replacing methanol can be of importance also in other proteomics methods, such as mixed cation exchange, using methanol under acidic conditions.

Urine and kidney cytokine profiles in experimental unilateral acute and chronic hydronephrosis.

OBJECTIVE: In search of potential urinary biomarkers of obstructive nephropathy, this study examined whether a potential change in the concentration of urinary cytokines [interferon-γ(IFN-γ), interleukin-1ß (IL-1ß), IL-2, IL-6, IL-10 and tumour necrosis factor-α (TNF-α)] reliably reflects changes in renal parenchymal levels of the same cytokines following the release of acute and chronic unilateral ureteral obstruction, respectively. MATERIAL AND METHODS: Acute obstruction was performed in 12 adult rats. After 48 h, six rats were used for selective urine collection and six rats had their kidneys removed and dissected into inner medulla and cortex. Chronic obstruction was performed in newborn rats. After 10 weeks, a similar set-up to that of the acute study was implemented. Sham-operated rats were prepared in parallel. Urine and tissue cytokines were measured with a bead-based multiplex sandwich immunoassay and analysed on a Luminex 100 IS instrument. RESULTS: In the acute study, there were significantly increased concentrations of IL-1ß and IL-6 in inner medulla and in urine from the obstructed kidney, significantly increased concentrations of TNF-α in urine from the obstructed kidney and, importantly, significantly increased levels of IL-10 in cortex and in urine from the non-obstructed kidney. In the chronic study, there were similar changes in IL-1ß and IL-6 (not significant) but no changes in TNF-α and IL-10. CONCLUSIONS: This study showed that inflammatory cytokines can be detected both in renal parenchyma and in urine from rats with experimental unilateral ureteral obstruction. Further studies are needed to confirm the diagnostic accuracy of IL-1ß, IL-6, IL-10 and TNF-α in urine.

The Hsp60-(p.V98I) mutation associated with hereditary spastic paraplegia SPG13 compromises chaperonin function both in vitro and in vivo.

We have previously reported the association of a mutation (c.292G > A/p.V98I) in the human HSPD1 gene that encodes the mitochondrial Hsp60 chaperonin with a dominantly inherited form of hereditary spastic paraplegia. Here, we show that the purified Hsp60-(p.V98I) chaperonin displays decreased ATPase activity and exhibits a strongly reduced capacity to promote folding of denatured malate dehydrogenase in vitro. To test its in vivo functions, we engineered a bacterial model system that lacks the endogenous chaperonin genes and harbors two plasmids carrying differentially inducible operons with human Hsp10 and wild-type Hsp60 or Hsp10 and Hsp60-(p.V98I), respectively. Ten hours after shutdown of the wild-type chaperonin operon and induction of the Hsp60-(p.V98I)/Hsp10 mutant operon, bacterial cell growth was strongly inhibited. No globally increased protein aggregation was observed, and microarray analyses showed that a number of genes involved in metabolic pathways, some of which are essential for robust aerobic growth, were strongly up-regulated in Hsp60-(p.V98I)-expressing bacteria, suggesting that the growth arrest was caused by defective folding of some essential proteins. Co-expression of Hsp60-(p.V98I) and wild-type Hsp60 exerted a dominant negative effect only when the chaperonin genes were expressed at relatively low levels. Based on our in vivo and in vitro data, we propose that the major effect of heterozygosity for the Hsp60-(p.V98I) mutation is a moderately decreased activity of chaperonin complexes composed of mixed wild-type and Hsp60-(p.V98I) mutant subunits.