Establishment of Motor Neuron-V3 Interneuron Progenitor Domain Boundary in Ventral Spinal Cord Requires Groucho-Mediated Transcriptional Corepression

Background: Dorsoventral patterning of the developing spinal cord is important for the correct generation of spinal neuronal types. This process relies in part on cross-repressive interactions between specific transcription factors whose expression is regulated by Sonic hedgehog. Groucho/transducin-like Enhancer of split (TLE) proteins are transcriptional corepressors suggested to be recruited by at least certain Sonic hedgehog-controlled transcription factors to mediate the formation of spatially distinct progenitor domains within the ventral spinal cord. The aim of this study was to characterize the involvement of TLE in mechanisms regulating the establishment of the boundary between the most ventral spinal cord progenitor domains, termed pMN and p3. Because the pMN domain gives rise to somatic motor neurons while the p3 domain generates V3 interneurons, we also examined the involvement of TLE in the acquisition of these neuronal fates. Methodology and Principal Findings: A combination of in vivo loss- and gain-of-function studies in the developing chick spinal cord was performed to characterize the role of TLE in ventral progenitor domain formation. It is shown here that TLE overexpression causes increased numbers of p3 progenitors and promotes the V3 interneuron fate while suppressing the motor neuron fate. Conversely, dominant-inhibition of TLE increases the numbers of pMN progenitors and postmitotic motor neurons. Conclusion: Based on these results, we propose that TLE is important to promote the formation of the p3 domain an

Distal truncation of KCC3 in non-French Canadian HMSN/ACC families

Hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC) is a severe and progressive autosomal recessive polyneuropathy. Mutations in the potassium-chloride cotransporter 3 gene (KCC3) were identified as responsible for HMSN/ACC in the French Canadian (FC) population. In the present study, the authors were interested in finding new mutations in non-FC populations, assessing the activity of mutant proteins and refining genotype-phenotype correlations. The authors screened KCC3 for mutations using direct sequencing in six non-FC HMSN/ACC families. They then assessed the functionality of the most common mutant protein using a flux assay in Xenopus laevis oocytes. The authors identified mutations in exon 22 of KCC3: a novel mutation (del + 2994-3003; E1015X) in one family, as well as a known mutation (3031C-->T; R1011X) found in five unrelated families and associated with two different haplotypes. The function of the cotransporter was abolished, although a limited amount of mutant proteins were correctly localized at the membrane. KCC3 mutations in exon 22 constitute a recurrent mutation site for hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC), regardless of ethnic origin, and are the most common cause of HMSN/ACC in the non-French Canadian (FC) families analyzed so far. Therefore, for genetic analysis, exon 22 screening should be prioritized in non-FC populations. Finally, the R1011X mutation leads to the abrogation of KCC3's function in Xenopus laevis oocytes, likely due to impaired transit of the cotransporter

Distal truncation of KCC3 in non-French Canadian HMSN/ACC families.

Item does not contain fulltextBACKGROUND: Hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC) is a severe and progressive autosomal recessive polyneuropathy. Mutations in the potassium-chloride cotransporter 3 gene (KCC3) were identified as responsible for HMSN/ACC in the French Canadian (FC) population. In the present study, the authors were interested in finding new mutations in non-FC populations, assessing the activity of mutant proteins and refining genotype-phenotype correlations. METHODS: The authors screened KCC3 for mutations using direct sequencing in six non-FC HMSN/ACC families. They then assessed the functionality of the most common mutant protein using a flux assay in Xenopus laevis oocytes. RESULTS: The authors identified mutations in exon 22 of KCC3: a novel mutation (del + 2994-3003; E1015X) in one family, as well as a known mutation (3031C-->T; R1011X) found in five unrelated families and associated with two different haplotypes. The function of the cotransporter was abolished, although a limited amount of mutant proteins were correctly localized at the membrane. CONCLUSIONS: KCC3 mutations in exon 22 constitute a recurrent mutation site for hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC), regardless of ethnic origin, and are the most common cause of HMSN/ACC in the non-French Canadian (FC) families analyzed so far. Therefore, for genetic analysis, exon 22 screening should be prioritized in non-FC populations. Finally, the R1011X mutation leads to the abrogation of KCC3's function in Xenopus laevis oocytes, likely due to impaired transit of the cotransporter

Kinetics of Zn2+ -induced Brain Type Creatine Kinase Unfolding and Aggregation.

We studied the effect of Zn2+ on the folding and aggregation of brain creatine kinase (CK-BB). We developed a method to purify CK-BB from rabbit brain and conducted inhibition kinetics and unfolding studies of CK-BB. Zn2+ conspicuously aggregated and osmolytes, such as glycine and proline, were able to suppress the formation of aggregates and protect the enzymatic activity against Zn2+. These results suggest that Zn2+ might act as a risk factor for CK-BB in the brain under certain conditions, and some osmolytes may help CK-BB to sustain the active state when Zn2+ is present. Our study provides useful information regarding the effect of Zn2+ on brain-derived metabolic enzymes, especially those that are putatively related to brain disease. Furthermore, our study suggests that although Zn2+ may induce CK-BB inactivation and misfolding, the ability of some abundant proteins and osmolytes to chelate Zn2+ nonspecifically may protect CK-BB and allow it to exist in the active formopen8

The advantage of channeling nucleotides for very processive functions

Nucleoside triphosphate (NTP)s, like ATP (adenosine 5’-triphosphate) and GTP (guanosine 5’-triphosphate), have long been considered sufficiently concentrated and diffusible to fuel all cellular ATPases (adenosine triphosphatases) and GTPases (guanosine triphosphatases) in an energetically healthy cell without becoming limiting for function. However, increasing evidence for the importance of local ATP and GTP pools, synthesised in close proximity to ATP- or GTP-consuming reactions, has fundamentally challenged our view of energy metabolism. It has become evident that cellular energy metabolism occurs in many specialised ‘microcompartments’, where energy in the form of NTPs is transferred preferentially from NTP-generating modules directly to NTP-consuming modules. Such energy channeling occurs when diffusion through the cytosol is limited, where these modules are physically close and, in particular, if the NTP-consuming reaction has a very high turnover, i.e. is very processive. Here, we summarise the evidence for these conclusions and describe new insights into the physiological importance and molecular mechanisms of energy channeling gained from recent studies. In particular, we describe the role of glycolytic enzymes for axonal vesicle transport and nucleoside diphosphate kinases for the functions of dynamins and dynamin-related GTPases