Biology subjects

Cao, M.

Publications and source records attributed to Cao, M..

7 recordsLinked to original sources

bioRxiv2018

Modeling motor neuron resilience in ALS using stem cells

Oculomotor neurons, which regulate eye movement, are resilient to degeneration in the lethal motor neuron disease amyotrophic lateral sclerosis (ALS). It would be highly advantageous if motor neuron resilience could be modeled in vitro. Towards this goal, we generated a high proportion of oculomotor neurons from mouse embryonic stem cells through temporal overexpression of Phox2a in neuronal progenitors. We demonstrate, using immunocytochemistry and RNA sequencing, that in vitro generated neurons are bona fide oculomotor neurons based on their similarity to their in vivo counterpart in rodent and man. We also show that in vitro generated oculomotor neurons display a robust activation of survival-promoting Akt signaling and are more resilient to the ALS-like toxicity of kainic acid than spinal motor neurons. Thus, we can generate bona fide oculomotor neurons in vitro which display a resilience similar to that seen in vivo.

neuroscience↗

bioRxiv2018

Inducible formation of leading cells driven by CD44 switching gives rise to collective invasion

Collective invasion into adjacent tissue is a hallmark of luminal breast cancer, with about 20% of cases that eventually undergo metastasis. It remained unclear how less aggressive luminal-like breast cancer transit to invasive cancer. Our study revealed that CD44hi cancer cells are the leading subpopulation in collective invading cancer cells, which could efficiently lead the collective invasion of CD44lo/follower cells. CD44hi/leading subpopulation showed specific gene signature of a cohort of hybrid epithelial/mesenchymal state genes and key functional co-regulators of collective invasion, which was distinct from CD44lo/follower cells. However, the CD44hi/leading cells, in partial-EMT state, were readily switching to CD44lo phenotype along with collective movements and vice versa, which is spontaneous and sensitive to tumor microenvironment. The CD44lo-to-CD44hi conversion is accompanied with a shift of CD44s-to-CD44v, but not corresponding to the conversion of non-CSC-to-CSC. Therefore, the CD44hi leader cells are not a stable subpopulation in breast tumors. This plasticity and ability to generate CD44hi carcinoma cells with enhanced invasion-initiating powers might be responsible for the transition from in situ to invasive behavior of luminal-type breast cancer.\n\nSignificanceNow, the mechanisms involved in local invasion and distant metastasis are still unclear. We identified a switch of CD44 that drives leader cell formation during collective invasion in luminal breast cancer. We provided evidence that interconversions between low and high CD44 states occur frequently during collective invasion. Furthermore, these findings demonstrated that the CD44hi/leader cells featuring partial EMT are inducible and attainable in response to tumor microenvironment. The CD44lo cancer cells are plastic that readily shift to CD44hi state, accompanied with shifts of CD44s-to-CD44v, thereby increasing tumorigenic and malignant potential. There are many \"non-invasiveness\" epithelial/follower cells with reversible invasive potential within an individual tumor, that casting some challenges on molecular targeting therapy.

cancer biology↗

bioRxiv2018

Heterogeneity of transposon expression and activation of the repressive network in human fetal germ cells

Epigenetic resetting in germ cells during development leads to the de-repression of transposable elements (TEs). piRNAs protect fetal germ cells from potentially harmful TEs by targeted destruction of mRNA and deposition of repressive epigenetic marks. Here we provide the first evidence for an active piRNA pathway and TE repression in germ cells of human fetal testis. We identify pre-pachytene piRNAs with features of secondary amplification that map most abundantly to L1 family TEs. We find that L1-ORF1p expression is heterogeneous in fetal germ cells, peaks at mid-gestation and declines concomitantly with increasing levels of piRNAs and H3K9me3, as well as nuclear localization of HIWI2. Surprisingly, following this decline, the same cells with accumulation of L1-ORF1p display highest levels of HIWI2 and H3K9me3, whereas L1-ORF1p low cells are also low in HIWI2 and H3K9me3. Conversely, earlier in development, the germ cells lacking L1-ORF1p express high levels of the chaperone HSP90a. We propose that a subset of HSP90a-armed germ cells resists L1 expression, whereas only those vulnerable L1-expressing germ cells activate the PIWI-piRNA repression pathway which leads to epigenetic silencing of L1 via H3K9me3.

developmental biology↗

bioRxiv2018

Spatial transcriptomics and in silico random pooling identify novel dopamine neuron subtype markers

Defining transcriptional profiles of substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) dopamine neurons is critical to understanding their differential vulnerability in Parkinsons Disease (PD). Here, we determine transcriptomes of human SNc and VTA dopamine neurons using LCM-seq on a large sample cohort. We apply a bootstrapping strategy as sample input to DESeq2 and identify 33 stably differentially expressed genes (DEGs) between these two subpopulations. We also compute a minimal sample size for identification of stable DEGs, which highlights why previous reported profiles from small sample sizes display extensive variability. Network analysis reveal gene interactions unique to each subpopulation and highlight differences in regulation of mitochondrial stability, apoptosis, neuronal survival, cytoskeleton regulation, extracellular matrix modulation and well as synapse integrity, which could explain the relative resilience of VTA dopamine neurons. Analysis of PD tissues showed that while identified stable DEGs can distinguish the subpopulations also in disease, the SNc markers SLIT1 and ATP2A3 were downregulated and thus appears to be biomarkers of disease. In summary, our study identifies human SNc and VTA marker profiles, which will be instrumental for studies aiming to modulate dopamine neuron resilience and to validate cell identity of stem cell-derived dopamine neurons.

neuroscience↗

bioRxiv2017

A Basal Ganglia Circuit Sufficient to Guide Birdsong Learning

Learning complex vocal behaviors, like speech and birdsong, is thought to rely on continued performance evaluation. Whether candidate performance evaluation circuits in the brain are sufficient to guide vocal learning is not known. Here, we test the sufficiency of VTA projections to the vocal basal ganglia (Area X) in singing zebra finches, a songbird species that learns to produce a complex and stereotyped multi-syllabic courtship song during development. We optogenetically manipulate VTA axon terminals in singing birds contingent on how the pitch of individual song syllables are naturally performed. We find that optical excitation and inhibition of VTA terminals have opponent effects on future performances of targeted song syllables and are each sufficient to reliably guide learned changes in song, consistent with positive and negative reinforcement of performance outcomes. These findings define a central role for reinforcement mechanisms in learning vocalizations and provide the first demonstration of minimal circuit elements for learning vocal behaviors.

neuroscience↗

bioRxiv2017

Cloning, Molecular Evolution And Functional Characterization Of ZmbHLH16, The Maize Ortholog Of OsTIP2 (OsbHLH142)

Abstract Basic helix-loop-helix (bHLH) transcription factors play key roles in plant male reproduction. More than 14 bHLH proteins related to pollen development have been cloned from rice and Arabidopsis. However, little is known about the role of the bHLH family in maize microspore development. In this study, the bHLH transcription factor ZmbHLH16 was cloned. ZmbHLH16 shares high similarity with the OsTIP2 (OsbHLH142) protein, a master regulator of the developmental coordination of male reproduction in rice. Expression characterization analysis showed that ZmbHLH16 is preferentially expressed in male reproductive organs and is located in the nucleus. Through nucleotide variation analysis, 36 polymorphic sites in ZmbHLH16, including 23 SNPs and 13 InDels, were detected among 78 maize inbred lines. Neutrality tests and linkage disequilibrium analysis showed that ZmbHLH16 experienced no significant evolutionary pressure. A yeast one-hybrid experiment showed that the first 80 residues in the N-terminus of ZmbHLH16 had transactivation activity, whereas the full length did not. To identify potential ZmbHLH16 interactors, 395 genes that shared similar expression patterns in a genome-wide search were obtained through coexpression analysis. Among these genes, the transcription factor ZmbHLH51 had an expression pattern and subcellular localization similar to those of ZmbHLH16. The interaction between ZmbHLH51 and ZmbHLH16 was verified in yeast cells. In addition to the typical bHLH domain, other regions of ZmbHLH16 were necessary and adequate for its heterodimerization with ZmbHLH51. Our results contribute to a solid foundation for further understanding the functions and mechanisms of ZmbHLH16.

molecular biology↗

bioRxiv2017

α7 nicotinic acetylcholine receptor signalling modulates the inflammatory and iron homeostasis in fetal brain microglia

Neuroinflammation in utero may result in life-long neurological disabilities. Microglia play a pivotal role, but the mechanisms are poorly understood. No early postnatal treatment strategies exist to enhance neuroprotective potential of microglia. We hypothesized that agonism on 7 nicotinic acetylcholine receptor (7nAChR) in fetal microglia will augment their neuroprotective transcriptome profile, while the antagonistic stimulation of 7nAChR will achieve the opposite. Using an in vivo - in vitro model of developmental programming of neuroinflammation induced by lipopolysaccharide (LPS), we validated this hypothesis in primary fetal sheep microglia cultures re-exposed to LPS in presence of a selective 7nAChR agonist or antagonist. Our RNAseq and protein level findings show that a pro-inflammatory microglial phenotype acquired in vitro by LPS stimulation is reversed with 7nAChR agonistic stimulation. Conversely, antagonistic 7nAChR stimulation potentiates the pro-inflammatory microglial phenotype. Surprisingly, under conditions of LPS double-hit an interference of a postulated 7nAChR - ferroportin signaling pathway may impede this mechanism. These results suggest a therapeutic potential of 7nAChR agonists in early re-programming of microglia in neonates exposed to in utero inflammation via an endogenous cerebral cholinergic anti-inflammatory pathway. Future studies will assess the role of interactions between inflammation-triggered microglial iron sequestering and 7nAChR signaling in neurodevelopment.

neuroscience↗