Combination of CD49b and CD229 Reveals a Subset of Multipotent Progenitors With Short-Term Activity Within the Hematopoietic Stem Cell Compartment

Hematopoiesis is maintained by hematopoietic stem cells (HSCs) that replenish all blood lineages throughout life. It is well-established that the HSC pool is functionally heterogeneous consisting of cells differing in longevity, self-renewal ability, cell proliferation, and lineage differentiation. Although HSCs can be identified through the Lineage-Sca-1+c-Kit+CD48-CD34-CD150+ immunophenotype, the cell surface marker combination does not permit absolute purification of functional HSCs with long-term reconstituting ability. Therefore, prospective isolation of long-term HSCs is crucial for mechanistic understanding of the biological functions of HSCs and for resolving functional heterogeneity within the HSC population. Here, we show that the combination of CD229 and CD49b cell surface markers within the phenotypic HSC compartment identifies a subset of multipotent progenitor (MPP) cells with high proliferative activity and short-term reconstituting ability. Thus, the addition of CD229 and CD49b to conventional HSC markers permits prospective isolation of functional HSCs by distinguishing MPPs in the HSC compartment.

CD49b identifies functionally and epigenetically distinct subsets of lineage-biased hematopoietic stem cells

Hematopoiesis is maintained by functionally diverse lineage-biased hematopoietic stem cells (HSCs). The functional significance of HSC heterogeneity and the regulatory mechanisms underlying lineage bias are not well understood. However, absolute purification of HSC subtypes with a pre-determined behavior remains challenging, highlighting the importance of continued efforts toward prospective isolation of homogeneous HSC subsets. In this study, we demonstrate that CD49b subdivides the most primitive HSC compartment into functionally distinct subtypes: CD49b⁻ HSCs are highly enriched for myeloid-biased and the most durable cells, while CD49b⁺ HSCs are enriched for multipotent cells with lymphoid bias and reduced self-renewal ability. We further demonstrate considerable transcriptional similarities between CD49b⁻ and CD49b⁺ HSCs but distinct differences in chromatin accessibility. Our studies highlight the diversity of HSC functional behaviors and provide insights into the molecular regulation of HSC heterogeneity through transcriptional and epigenetic mechanisms.

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CD49b⁻ HSCs are highly enriched for durable and long-term myeloid-biased HSCs

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CD49b⁺ HSCs are enriched for less durable cells with lymphoid bias

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CD49b⁻ and CD49b⁺ HSCs are transcriptionally similar but epigenetically distinct

Dihydroceramide desaturase regulates the compartmentalization of Rac1 for neuronal oxidative stress

Disruption of sphingolipid homeostasis is known to cause neurological disorders, but the mechanisms by which specific sphingolipid species modulate pathogenesis remain unclear. The last step of de novo sphingolipid synthesis is the conversion of dihydroceramide to ceramide by dihydroceramide desaturase (human DEGS1; Drosophila Ifc). Loss of ifc leads to dihydroceramide accumulation, oxidative stress, and photoreceptor degeneration, whereas human DEGS1 variants are associated with leukodystrophy and neuropathy. In this work, we demonstrate that DEGS1/ifc regulates Rac1 compartmentalization in neuronal cells and that dihydroceramide alters the association of active Rac1 with organelle-mimicking membranes. We further identify the Rac1-NADPH oxidase (NOX) complex as the major cause of reactive oxygen species (ROS) accumulation in ifc-knockout (ifc-KO) photoreceptors and in SH-SY5Y cells with the leukodystrophy-associated DEGS1^H132R variant. Suppression of Rac1-NOX activity rescues degeneration of ifc-KO photoreceptors and ameliorates oxidative stress in DEGS1^H132R-carrying cells. Therefore, we conclude that DEGS1/ifc deficiency causes dihydroceramide accumulation, resulting in Rac1 mislocalization and NOX-dependent neurodegeneration.

Chondroitin sulfate proteoglycan Windpipe modulates Hedgehog signaling in Drosophila

Proteoglycans, a class of carbohydrate-modified proteins, often modulate growth factor signaling on the cell surface. However, the molecular mechanism by which proteoglycans regulate signal transduction is largely unknown. In this study, using a recently developed glycoproteomic method, we found that Windpipe (Wdp) is a novel chondroitin sulfate proteoglycan (CSPG) in Drosophila. Wdp is a single-pass transmembrane protein with leucin-rich repeat (LRR) motifs and bears three CS sugar chain attachment sites in the extracellular domain. Here we show that Wdp modulates the Hedgehog (Hh) pathway. In the wing disc, overexpression of wdp inhibits Hh signaling, which is dependent on its CS chains and the LRR motifs. The wdp null mutant flies show a specific defect (supernumerary scutellar bristles) known to be caused by Hh overexpression. RNA interference knockdown and mutant clone analyses showed that loss of wdp leads to the up-regulation of Hh signaling. Altogether, our study demonstrates a novel role of CSPGs in regulating Hh signaling.

Clinical trial of electrical acupuncture on hemiplegic stroke patients

To assess the efficacy of electrical acupuncture in the rehabilitation of patients with hemiplegia in stroke, we randomized 128 patients within 2 wk of stroke onset to receive either comprehensive rehabilitation plus electrical acupuncture (n = 59) or comprehensive rehabilitation only (n = 59). Electrical acupuncture was administered by electrical stimulation of acupuncture points through adhesive surface electrodes five times per week. Neurological status (Brunnstrom's stage) and the Chinese version of the Functional Independence Measure were assessed before treatment and at discharge. Patients treated with electrical acupuncture had a shorter duration of hospital stay for rehabilitation and better neurological and functional outcomes than the control group had, with a significant difference in scores for self-care and locomotion (P = 0.02). This result did not postulate the previous study that acupuncture therapy for stroke patients should depend on needle manual and "de qi" response. We suggest that electrical acupuncture through adhesive surface electrodes in conjunction with current optimal rehabilitation programs is a convenient and effective therapy for stroke patients.