- EPG5 c.1007A > G mutation in a sibling pair with rapidly progressing Vici syndrome. [Journal Article]
- AHAnn Hum Genet 2019 Jun 11
- We report on a sibling pair with the EPG5 c.1007A > G mutation who developed a severe form of Vici syndrome and died in infancy. The c.1007A > G (p.Gln336Arg) mutation, affecting the penultimate nucl…
We report on a sibling pair with the EPG5 c.1007A > G mutation who developed a severe form of Vici syndrome and died in infancy. The c.1007A > G (p.Gln336Arg) mutation, affecting the penultimate nucleotide and the splicing of exon 2 is the most common mutation of EPG5 and is typically associated with a less devastating prognosis: cardiomyopathy and cataract are less frequent consequences and the median survival time is 78 months compared to an overall median survival of 42 months. The less severe course related to c.1007A > G was formerly explained by the preserved canonical splicing in 25% of the transcripts. In contrast, we found the messenger RNA encoded by the c.1007A > G allele to be absent, explaining the severe course of the disease. This family provides another example of phenotypic variability related to a differential splicing.
- Critical Considerations in Genetic Counseling of Patients With the NPHS2 R229Q Variant. [Letter]
- AJAm J Kidney Dis 2019; 73(4):576
- The Zebrafish as an Emerging Model to Study DNA Damage in Aging, Cancer and Other Diseases. [Journal Article]
- FCFront Cell Dev Biol 2018; 6:178
- Cancer is a disease of the elderly, and old age is its largest risk factor. With age, DNA damage accumulates continuously, increasing the chance of malignant transformation. The zebrafish has emerged…
Cancer is a disease of the elderly, and old age is its largest risk factor. With age, DNA damage accumulates continuously, increasing the chance of malignant transformation. The zebrafish has emerged as an important vertebrate model to study these processes. Key mechanisms such as DNA damage responses and cellular senescence can be studied in zebrafish throughout its life course. In addition, the zebrafish is becoming an important resource to study telomere biology in aging, regeneration and cancer. Here we review some of the tools and resources that zebrafish researchers have developed and discuss their potential use in the study of DNA damage, cancer and aging related diseases.
- The swimming plus-maze test: a novel high-throughput model for assessment of anxiety-related behaviour in larval and juvenile zebrafish (Danio rerio). [Journal Article]
- SRSci Rep 2018 Nov 08; 8(1):16590
- Larval zebrafish (Danio rerio) has the potential to supplement rodent models due to the availability of resource-efficient, high-throughput screening and high-resolution imaging techniques. Although …
Larval zebrafish (Danio rerio) has the potential to supplement rodent models due to the availability of resource-efficient, high-throughput screening and high-resolution imaging techniques. Although behavioural models are available in larvae, only a few can be employed to assess anxiety. Here we present the swimming plus-maze (SPM) test paradigm, a tool to assess anxiety-related avoidance of shallow water bodies in early developmental stages. The "+" shaped apparatus consists of arms of different depth, representing different levels of aversiveness similarly to the rodent elevated plus-maze. The paradigm was validated (i) in larval and juvenile zebrafish, (ii) after administration of compounds affecting anxiety and (iii) in differentially aversive experimental conditions. Furthermore, we compared the SPM with conventional "anxiety tests" of zebrafish to identify their shared characteristics. We have clarified that the preference of deeper arms is ontogenetically conserved and can be abolished by anxiolytic or enhanced by anxiogenic agents, respectively. The behavioural readout is insensitive to environmental aversiveness and is unrelated to behaviours assessed by conventional tests involving young zebrafish. Taken together, we have developed a sensitive high-throughput test allowing the assessment of anxiety-related responses of zebrafish regardless of developmental stage, granting the opportunity to combine larva-based state-of-the-art methods with detailed behavioral analysis.
- The mutation-dependent pathogenicity of NPHS2 p.R229Q: A guide for clinical assessment. [Journal Article]
- HMHum Mutat 2018; 39(12):1854-1860
- NPHS2, encoding podocin, is the major gene implicated in steroid-resistant nephrotic syndrome. Its c.686G>A, p.R229Q variant is the first human variant with a mutation-dependent pathogenicity; it is …
NPHS2, encoding podocin, is the major gene implicated in steroid-resistant nephrotic syndrome. Its c.686G>A, p.R229Q variant is the first human variant with a mutation-dependent pathogenicity; it is only pathogenic when trans-associated to specific mutations. Secondary to its high allele frequency in the European, South Asian, African, and Latino populations, its benign trans-associations can be accidentally identified in affected patients. Distinguishing pathogenic and benign p.R229Q associations can be challenging. In this paper, we present the currently known pathogenic and benign associations, and show that a rare p.R229Q association can be considered pathogenic if the variant in trans meets the following criteria; it affects the 270-351 residues and alters but does not disrupt the oligomerization, its p.R229Q association is found in a family with slowly progressing focal segmental glomerulosclerosis, but is expected to be rare in the general population (<1:106). We show that >15% of the p.R229Q associations identified so far in patients are benign.
- Comprehensive genetic testing in children with a clinical diagnosis of ARPKD identifies phenocopies. [Journal Article]
- PNPediatr Nephrol 2018; 33(10):1713-1721
- CONCLUSIONS: We found all ARPKD cases without PKHD1 point mutations to be phenocopies, and none to be explained by biallelic PKHD1 copy number variations. Screening for copy number variations is recommended in patients with a heterozygous point mutation.
- Zebrafish Models of Rare Hereditary Pediatric Diseases. [Review]
- DDiseases 2018 May 22; 6(2)
- Recent advances in sequencing technologies have made it significantly easier to find the genetic roots of rare hereditary pediatric diseases. These novel methods are not panaceas, however, and they o…
Recent advances in sequencing technologies have made it significantly easier to find the genetic roots of rare hereditary pediatric diseases. These novel methods are not panaceas, however, and they often give ambiguous results, highlighting multiple possible causative mutations in affected patients. Furthermore, even when the mapping results are unambiguous, the affected gene might be of unknown function. In these cases, understanding how a particular genotype can result in a phenotype also needs carefully designed experimental work. Model organism genetics can offer a straightforward experimental setup for hypothesis testing. Containing orthologs for over 80% of the genes involved in human diseases, zebrafish (Danio rerio) has emerged as one of the top disease models over the past decade. A plethora of genetic tools makes it easy to create mutations in almost any gene of the zebrafish genome and these mutant strains can be used in high-throughput preclinical screens for active molecules. As this small vertebrate species offers several other advantages as well, its popularity in biomedical research is bound to increase, with "aquarium to bedside" drug development pipelines taking a more prevalent role in the near future.
- C-terminal oligomerization of podocin mediates interallelic interactions. [Journal Article]
- BBBiochim Biophys Acta Mol Basis Dis 2018; 1864(7):2448-2457
- Interallelic interactions of membrane proteins are not taken into account while evaluating the pathogenicity of sequence variants in autosomal recessive disorders. Podocin, a membrane-anchored compon…
Interallelic interactions of membrane proteins are not taken into account while evaluating the pathogenicity of sequence variants in autosomal recessive disorders. Podocin, a membrane-anchored component of the slit diaphragm, is encoded by NPHS2, the major gene mutated in hereditary podocytopathies. We formerly showed that its R229Q variant is only pathogenic when trans-associated to specific 3' mutations and suggested the causal role of an abnormal C-terminal dimerization. Here we show by FRET analysis and size exclusion chromatography that podocin oligomerization occurs exclusively through the C-terminal tail (residues 283-382): principally through the first C-terminal helical region (H1, 283-313), which forms a coiled coil as shown by circular dichroism spectroscopy, and through the 332-348 region. We show the principal role of the oligomerization sites in mediating interallelic interactions: while the monomer-forming R286Tfs*17 podocin remains membranous irrespective of the coexpressed podocin variant identity, podocin variants with an intact H1 significantly influence each other's localization (r2 = 0.68, P = 9.2 × 10-32). The dominant negative effect resulting in intracellular retention of the pathogenic F344Lfs*4-R229Q heterooligomer occurs in parallel with a reduction in the FRET efficiency, suggesting the causal role of a conformational rearrangement. On the other hand, oligomerization can also promote the membrane localization: it can prevent the endocytosis of F344Lfs*4 or F344* podocin mutants induced by C-terminal truncation. In conclusion, C-terminal oligomerization of podocin can mediate both a dominant negative effect and interallelic complementation. Interallelic interactions of NPHS2 are not restricted to the R229Q variant and have to be considered in compound heterozygous individuals.
- Endoplasmic reticulum-retained podocin mutants are massively degraded by the proteasome. [Journal Article]
- JBJ Biol Chem 2018 03 16; 293(11):4122-4133
- Podocin is a key component of the slit diaphragm in the glomerular filtration barrier, and mutations in the podocin-encoding gene NPHS2 are a common cause of hereditary steroid-resistant nephrotic sy…
Podocin is a key component of the slit diaphragm in the glomerular filtration barrier, and mutations in the podocin-encoding gene NPHS2 are a common cause of hereditary steroid-resistant nephrotic syndrome. A mutant allele encoding podocin with a p.R138Q amino acid substitution is the most frequent pathogenic variant in European and North American children, and the corresponding mutant protein is poorly expressed and retained in the endoplasmic reticulum both in vitro and in vivo To better understand the defective trafficking and degradation of this mutant, we generated human podocyte cell lines stably expressing podocinwt or podocinR138Q Although it has been proposed that podocin has a hairpin topology, we present evidence for podocinR138QN-glycosylation, suggesting that most of the protein has a transmembrane topology. We find that N-glycosylated podocinR138Q has a longer half-life than non-glycosylated podocinR138Q and that the latter is far more rapidly degraded than podocinwt Consistent with its rapid degradation, podocinR138Q is exclusively degraded by the proteasome, whereas podocinwt is degraded by both the proteasomal and the lysosomal proteolytic machineries. In addition, we demonstrate an enhanced interaction of podocinR138Q with calnexin as the mechanism of endoplasmic reticulum retention. Calnexin knockdown enriches the podocinR138Q non-glycosylated fraction, whereas preventing exit from the calnexin cycle increases the glycosylated fraction. Altogether, we propose a model in which hairpin podocinR138Q is rapidly degraded by the proteasome, whereas transmembrane podocinR138Q degradation is delayed due to entry into the calnexin cycle.
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- The Doctor of Delayed Publications: The Remarkable Life of George Streisinger (1927-1984). [Historical Article]
- ZZebrafish 2018; 15(3):314-319
- The history of science offers multiple examples of how the perseverance of a single visionary person could open the floodgates for a whole new area of research. Zebrafish research is one of these fie…
The history of science offers multiple examples of how the perseverance of a single visionary person could open the floodgates for a whole new area of research. Zebrafish research is one of these fields with an exciting founding story, as it was the dogged persistence of one man, George Streisinger, that ultimately lifted this little fish out of the obscurity of pet shops into the pantheon of genetic model organisms. The Hungarian born Streisinger was one of the most gifted geneticists of his era and his network of mentors and friends really reads like a who-is-who of 20th century genetics. And it was not only science where he excelled: the way he took his civic duties seriously and outspokenly fought social injustice wherever he met it offers an important lesson on integrity for today's scientists as well.