We report that prospectively isolated, human CNS stem cells grown as neurospheres (hCNS-SCns) survive, migrate, and express differentiation markers for neurons and oligodendrocytes after longterm engraftment in spinal cord-injured NOD-scid mice. hCNS-SCns engraftment was associated with locomotor recovery, an observation that was abolished by selective ablation of engrafted cells by diphtheria toxin. Remyelination by hCNS-SCns was found in both the spinal cord injury NOD-scid model and myelin-deficient shiverer mice. Moreover, electron microscopic evidence consistent with synapse formation between hCNS-SCns and mouse host neurons was observed. Glial fibrillary acidic protein-positive astrocytic differentiation was rare, and hCNS-SCns did not appear to contribute to the scar. These data suggest that hCNS-SCns may possess therapeutic potential for CNS injury and disease.behavioral assessment ͉ differentiation ͉ stem cell transplantation R ecent studies have used a variety of immortalized, engineered, or isolated rodent-derived precursor͞stem cells transplanted into rodent models of spinal cord injury. Many of these studies focused on cell survival and did not address differentiation, functional recovery, or the causal relationship between successful engraftment and observed behavioral improvements. When differentiation was investigated, embryonic and adult neural stem cells were reported to principally assume glial fibrillary acidic protein (GFAP)-positive astrocytic phenotypes after grafting into nonneurogenic regions of uninjured adult CNS (1, 2) or injured spinal cord (3-5). Furthermore, although in vitro predifferentiation paradigms designed to generate neural lineage restricted precursors successfully generated ␤-tubulin III (Tuj-1)-positive neuronal phenotypes either in vitro or after transplantation into uninjured spinal cord, this commitment was overridden by environmental cues in the injured spinal cord (6).Transplants of human brain-derived stem cells or human spinal cord tissue into injured rat spinal cord have been described (7-9). Moreover, several human cell transplantation paradigms recently have been reported to promote locomotor recovery: human umbilical cell infusion in a rat spinal cord injury model, although only within 3 weeks or less postgrafting (10); neurons differentiated in vitro under retinoic acid from human embryonal teratocarcinoma cells and transplanted into a rat spinal cord injury model (11); human ES cells differentiated in vitro to oligoprogenitors and transplanted into a rat spinal cord injury model (12); and human neural stem͞progenitor cells transplanted into a monkey spinal cord injury model (13). In general, these studies lack some or all of the following: definitive identification of transplanted cells, longterm survival and engraftment data, evidence of differentiation, and͞or direct evidence of functional integration of human cells in the injured spinal cord. The current study addresses three previously unexplored issues in stem cell transplantation research for spinal co...

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Of the eight nuclear genes in the plant multi‐gene family which encodes the small subunit (rbcS) of Petunia (Mitchell) ribulose bisphosphate carboxylase, one rbcS gene accounts for 47% of the total rbcS gene expression in petunia leaf tissue. Expression of each of five other rbcS genes is detected at levels between 2 and 23% of the total rbcS expression in leaf tissue, while expression of the remaining two rbcS genes is not detected. There is considerable variation (500‐fold) in the levels of total rbcS mRNA in six organs of petunia (leaves, sepals, petals, stems, roots and stigmas/anthers). One gene, SSU301, showed the highest levels of steady‐state mRNA in each of the organs examined. We discuss the differences in the steady‐state mRNA levels of the individual rbcS genes in relation to their gene structure, nucleotide sequence and genomic linkage.