CNS axons globally increase axonal transport after peripheral conditioning.

Despite the inability of CNS axons to regenerate, an increased regenerative capacity can be elicited following conditioning lesion to the peripheral branch of dorsal root ganglia neurons (DRGs). By in vivo radiolabeling of rat DRGs, coupled to mass spectrometry and kinesin immunoprecipitation of spinal cord extracts, we determined that the anterograde transport of cytoskeleton components, metabolic enzymes and axonal regeneration enhancers, was increased in the central branch of DRGs following a peripheral conditioning lesion. Axonal transport of mitochondria was also increased in the central branch of Thy1-MitoCFP mice following a peripheral injury. This effect was generalized and included augmented transport of lysosomes and synaptophysin- and APP-carrying vesicles. Changes in axonal transport were only elicited by a peripheral lesion and not by spinal cord injury. In mice, elevated levels of motors and of polyglutamylated and tyrosinated tubulin were present following a peripheral lesion and can explain the increase in axonal transport induced by conditioning. In summary, our work shows that a peripheral injury induces a global increase in axonal transport that is not restricted to the peripheral branch, and that, by extending to the central branch, allows a rapid and sustained support of regenerating central axons.

Novel mutations in the CLN6 gene causing a variant late infantile neuronal ceroid lipofuscinosis.

The neuronal ceroid lipofuscinoses (NCLs) are a heterogeneous group of autosomal recessive neurodegenerative diseases comprising Batten and other related diseases plus numerous variants. They are characterized by progressive neuronal cell death. The CLN6 gene was recently identified, mutations in which cause one of the variant late infantile forms of NCL (vLINCL). We describe four novel mutations in the CLN6 gene. This brings the total number of CLN6 mutations known to 11 in 38 families. This suggests that the CLN6 gene may be highly mutable. An American patient of Irish/French/Native American origin was heterozygous for a 4-bp insertion (c.267_268insAACG) in exon 3. The other allele had a point mutation (c.898T>C) in exon 7 resulting in a W300R amino acid change. Two Trinidadian siblings of Indian origin were homozygous for a mutation at the 5' donor splice site of exon 4 (IVS4+1G>T), affecting the first base of the invariant GT at the beginning of intron 4. The fourth novel mutation, a double deletion of 4 bp and 1 bp in exon 7 (c.829_832delGTCG;c.837delG), was identified in a Portuguese patient heterozygous for the I154del Portuguese CLN6 mutation. Four of the 11 mutations identified are in exon 4. Three Portuguese patients with clinical profiles similar to CLN6 patients without defects in CLN6 or other known NCL genes are described. We conclude the following: 1) the CLN6 gene may be a highly mutable gene; 2) exon 4 must code for a segment of the protein crucial for function; 3) vLINCL disease in Portugal is genetically heterogeneous; 4) the I154del accounts for 81.25% of affected CLN6 Portuguese alleles; and 5) three vLINCL Portuguese patients may have defects in a new NCL gene.