Unexpected rescue of alpha-synuclein and multimerin1 deletion in C57BL/6JOlaHsd mice by beta-adducin knockout

Automated Capillary Electrophoresis Immunoblot for the Detection of Alpha-Synuclein in Mouse Tissue

Background

Alpha-synuclein (aSyn) is a key player in neurodegenerative diseases such as Parkinson's disease (PD), dementia with Lewy bodies, or multiple system atrophy. aSyn is expressed throughout the brain, and can also be detected in various peripheral tissues. In fact, initial symptoms of PD are non-motoric and include autonomic dysfunction, suggesting that the periphery might play an important role in early development of the disease. aSyn is expressed at relatively low levels in non-central tissues, which brings challenges for its detection and quantification in different tissues.

Objective

Our goal was to assess the sensitivity of aSyn detection in central and peripheral mouse tissues through capillary electrophoresis (CE) immunoblot, considering the traditional SDS-PAGE immunoblot as the current standard.

Methods

Tissues from central and non-central origin from wild type mice were extracted, and included midbrain, inner ear, and esophagus/stomach. aSyn detection was assessed through immunoblotting using Simple Western size-based CE and SDS-PAGE.

Results

CE immunoblots show a consistent detection of aSyn in central and peripheral tissues. Through SDS-PAGE, immunoblots revealed a reliable signal corresponding to aSyn, particularly following membrane fixation.

Conclusion

Our results suggest a reliable detection of aSyn in central and peripheral tissues using the CE Simple Western immunoblot system. These observations can serve as preliminary datasets when aiming to formally compare CE with SDS-PAGE, as well as for further characterization of aSyn using this technique.

CRB1 is required for recycling by RAB11A+ vesicles in human retinal organoids

CRB1 gene mutations can cause early- or late-onset retinitis pigmentosa, Leber congenital amaurosis, or maculopathy. Recapitulating human CRB1 phenotypes in animal models has proven challenging, necessitating the development of alternatives. We generated human induced pluripotent stem cell (iPSC)-derived retinal organoids of patients with retinitis pigmentosa caused by biallelic CRB1 mutations and evaluated them against autologous gene-corrected hiPSCs and hiPSCs from healthy individuals. Patient organoids show decreased levels of CRB1 and NOTCH1 expression at the retinal outer limiting membrane. Proximity ligation assays show that human CRB1 and NOTCH1 can interact via their extracellular domains. CRB1 patient organoids feature increased levels of WDFY1+ vesicles, fewer RAB11A+ recycling endosomes, decreased VPS35 retromer complex components, and more degradative endolysosomal compartments relative to isogenic control organoids. Taken together, our data demonstrate that patient-derived retinal organoids enable modeling of retinal degeneration and highlight the importance of CRB1 in early endosome maturation receptor recycling in the retina.

Mild reproductive impact of a Y chromosome deletion on a C57BL/6J substrain

A recently reported deletion of about 40 Mb in length between 6.12/6.57 and 46.73/47.31 Mb on the Y chromosome long arm of the C57BL/6JBomTac inbred strain made us closely examine the strain’s breeding history and reproductive characteristics. We verified that the two copies of Rbm31y that are present inside the putative deletion were indeed deleted. This inbred strain presents an expected litter size for a C57BL/6 substrain. In vitro fertilization (IVF) efficiency and breeding efficiencies are comparable to those of the C57BL/6NTac substrain; however, the male/female sex ratio in the C57BL/6JBomTac is mildly skewed towards females. There is an increase in the percentage of sperm shape abnormalities found in C57BL/6JBomTac (35%) versus C57BL/6NTac (11%). The most frequent type of sperm abnormality observed is bent heads (19%). Additionally, there is deregulation of several transcripts expressed in the testes. We determined that this mutation arose in the C57BL/6JBomTac Foundation Colony in 2008, and it was completely fixed in the colony by 2009.

A spontaneous deletion of α-synuclein is associated with an increase in CB1 mRNA transcript and receptor expression in the hippocampus and amygdala: effects on alcohol consumption

α-Synuclein (α-syn) protein and endocannabinoid CB1 receptors are primarily located in presynaptic terminals. An association between α-syn and CB1 receptors has recently been established in Parkinson's disease, but it is completely unknown whether there is an association between these two proteins in alcohol addiction. Therefore, we aimed to examine the α-syn mRNA transcript and protein expression levels in the prefrontal cortex, striatum, amygdala and hippocampus. These brain regions are the most frequently implicated in alcohol and other drug addiction. In these studies, we used C57BL/6 mice carrying a spontaneous deletion of the α-syn gene (C57BL/6(Snca-/-) ) and their respective controls (C57BL/6(Snca) (+/) (+) ). These animals were monitored for spontaneous alcohol consumption (3-10%) and their response to a hypnotic-sedative dose of alcohol (3 g kg(-1) ) was also assessed. Compared with the C57BL/6(Snca+/+) mice, we found that the C57BL/6(Snca-/-) mice exhibited a higher expression level of the CB1 mRNA transcript and CB1 receptor in the hippocampus and amygdala. Furthermore, C57BL/6(Snca-/-) mice showed an increase in alcohol consumption when offered a 10% alcohol solution. There was no significant difference in sleep time after the injection of 3 g/kg alcohol. These results are the first to reveal an association between α-syn and the CB1 receptor in the brain regions that are most frequently implicated in alcohol and other drug addictions.

Alpha-synuclein deficiency in the C57BL/6JOlaHsd strain does not modify disease progression in the ME7-model of prion disease

We previously detailed how intrahippocampal inoculation of C57BL/6J mice with murine modified scrapie (ME7) leads to chronic neurodegeneration (Cunningham C, Deacon R, Wells H, Boche D, Waters S, Diniz CP, Scott H, Rawlins JN, Perry VH (2003) Eur J Neurosci 17:2147-2155.). Our characterization of the ME7-model is based on inoculation of this murine modified scrapie agent into C57BL/6J mice from Harlan laboratories. This agent in the C57BL/6J host generates a disease that spans a 24-week time course. The hippocampal pathology shows progressive misfolded prion (PrP(Sc)) deposition, astrogliosis and leads to behavioural dysfunction underpinned by the early synaptic loss that precedes neuronal death. The Harlan C57BL/6J, although widely used as a wild type mouse, are a sub-strain harbouring a spontaneous deletion of alpha-synuclein with the full description C57BL/6JOlaHsd. Recently alpha-synuclein has been shown to ameliorate the synaptic loss in a mouse model lacking the synaptic chaperone CSP-alpha. This opens a potential confound of the ME7-model, particularly with respect to the signature synaptic loss that underpin the physiological and behavioural dysfunction. To investigate if this strain-selective loss of a candidate disease modifier impacts on signature ME7 pathology, we compared cohorts of C57BL/6JOlaHsd (alpha-synuclein negative) with the founder strain from Charles Rivers (C57BL/6JCrl, alpha-synuclein positive). There were subtle changes in behaviour when comparing control animals from the two sub-strains indicating potentially significant consequences for studies assuming neurobiogical identity of both strains. However, there was no evidence that the absence of alpha-synuclein modifies disease. Indeed, accumulation of PrP(Sc), synaptic loss and the behavioural dysfunction associated with the ME7-agent was the same in both genetic backgrounds. Our data suggest that alpha-synuclein deficiency does not contribute to the compartment specific processes that give rise to prion disease mediated synaptotoxicity and neurodegeneration.

Genomic investigation of alpha-synuclein multiplication and parkinsonism

OBJECTIVE

Copy number variation is a common polymorphic phenomenon within the human genome. Although the majority of these events are non-deleterious they can also be highly pathogenic. Herein we characterize five families with parkinsonism that have been identified to harbor multiplication of the chromosomal 4q21 locus containing the alpha-synuclein gene (SNCA).

METHODS

A methodological approach using fluorescent in situ hybridization and Affymetrix (Santa Clara, CA) 250K SNP microarrays was used to characterize the multiplication in each family and to identify the genes encoded within the region. The telomeric and centromeric breakpoints of each family were further narrowed using semiquantitative polymerase chain reaction with microsatellite markers and then screened for transposable repeat elements.

RESULTS

The severity of clinical presentation is correlated with SNCA dosage and does not appear to be overtly affected by the presence of other genes in the multiplicated region. With the exception of the Lister kindred, in each family the multiplication event appears de novo. The type and position of Alu/LINE repeats are also different at each breakpoint. Microsatellite analysis demonstrates two genomic mechanisms are responsible for chromosome 4q21 multiplications, including both SNCA duplication and recombination.

INTERPRETATION

SNCA dosage is responsible for parkinsonism, autonomic dysfunction, and dementia observed within each family. We hypothesize dysregulated expression of wild-type alpha-synuclein results in parkinsonism and may explain the recent association of common SNCA variants in sporadic Parkinson's disease. SNCA genomic duplication results from intraallelic (segmental duplication) or interallelic recombination with unequal crossing over, whereas both mechanisms appear to be required for genomic SNCA triplication.

Quiet mutations in inbred strains of mice

The year 2009 is the 100th anniversary of the founding of the first inbred strain of mouse, called DBA. During the last 100 years, inbred strains have proved their value for biomedical research and the number of such strains has mushroomed to over 450, each with different genotypic and phenotypic characteristics and useful for the study of disease and normal function. However, although inbred strains are stable, they are not fixed entities and researchers need to be aware of the phenomena of new mutations and of genetic drift, which occur within all mouse colonies. If the mutations are what we term in this review 'quiet mutations', then they might result in rather unexpected and sometimes tremendously valuable results. Here, we discuss these phenomena and look at how new genomic technologies might help us to detect 'quiet mutations' and use them to our advantage.