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Hereditary spastic paraplegias (HSPs) represent a clinically and genetically heterogeneous group of diseases. Major symptoms comprise progressive bilateral leg stiffness, spasticity at rest and diffuse muscle weakness. Complex forms are characterized by additional symptoms like dementia, cerebellar dysfunction or seizures. Autosomal dominant, autosomal recessive, X-linked recessive and possibly mitochondrial inheritance have been described in familial HSP. The most frequently mutated gene in familial cases of uncomplicated autosomal dominant HSP is SPAST, however de novo mutations in SPAST are rarely found. Here, we report on the clinical and genetic findings in a family with three children afflicted by complex HSP and their unaffected parents. Although autosomal dominant inheritance seemed unlikely in this family, genetic testing revealed a novel SPAST mutation, c.1837G>C (p.Asp613His), in a heterozygous state in all affected individuals and somatic mosaicism of this mutation in the unaffected mother. Our study thus expands the knowledge on SPAST-associated HSP and emphasizes that de novo mutations and somatic mosaicism should be taken into consideration in HSP families presenting with a family history not suggestive for an autosomal dominant inheritance pattern.

Differences in fusion activity between measles virus (MV) attenuated, oncolytic strain MVNSe and pathogenic MVwt323 are reflected in amino acid 94 of the fusion (F) proteins. A valine 94 in FNSe (naturally) or Fwt323 (introduced) correlated with enhanced cell–cell fusion activity during transient glycoprotein expression or recombinant MV infections irrespective of the strains’ targeted receptors, whereas the reverse effect was found for methionine 94. Enhanced fusogenicity was determined by weaker glycoprotein interaction and correlated positively with cytotoxicity in both virus strains. Amino acid 94 of F can be used to tailor fusogenicity and cytotoxicity of recombinant MV, while the cellular receptor triggering fusion is not decisive.

In the present paper we describe a rapid and sensitive method for the simultaneous isolation of total RNA and genomic plus low-molecular-weight DNA from apoptotic cells. Using this method, we were able to detect a DNA ladder from as low as 30,000 apoptotic cells in only 45 min including gel electrophoresis. In addition, RNA can be readily obtained from the same specimen to assess gene expression during apoptosis. This method therefore appears to be advantageous when sensitivity and low amounts of sample material are a limiting factor.

Type I and III interferon-regulated Mx genes encode evolutionary conserved antiviral restriction factors which inhibit a broad range of RNA viruses in most vertebrate species. In mice, the Mx1 locus confers resistance to members of the Orthomyxoviridae, such as influenza A and Thogoto viruses. Mice of strain A2G carry a functional Mx1 gene, while most other laboratory inbred mouse strains carry truncated and therefore defective Mx1 alleles. A recent study (Ferris MT et al. PLOS pathogens 9(2) 2013) investigating how genetic factors might contribute to influenza susceptibility showed that CAST/EiJ mice, an inbred strain derived from wild Mus musculus castaneus, are susceptible to influenza virus challenge although they carry a full-length Mx1 gene. Here we characterized CAST-derived Mx1 in order to better understand the molecular basis of its altered antiviral properties. We were able to show that CAST-derived Mx1 retains a low degree of anti-influenza activity but, surprisingly, is still able to confer full protection against Thogoto virus challenge. Sequencing revealed that CAST-derived Mx1 differs by two amino acids from A2G-derived Mx1 which are both localized in the GTPase (G) domain of the protein. These mutations lead to a reduction in GTPase activity. They further diminish Mx1 protein levels in organs of animals after interferon stimulation in vivo. Interestingly, these mutations have no effect on mRNA levels, suggesting that the reduced Mx1 protein levels might be attributed to differences in protein stability. In summary, our findings are able to explain the unexpected virus susceptibility of CAST/EiJ mice.