The centromere, which is one of the essential parts of a chromosome, controls kinetochore formation and chromosome segregation during mitosis and meiosis. While centromere function is conserved in eukaryotes, the cent...The centromere, which is one of the essential parts of a chromosome, controls kinetochore formation and chromosome segregation during mitosis and meiosis. While centromere function is conserved in eukaryotes, the centromeric DNA sequences evolve rapidly and have few similarities among species. The histone H3 variant CENH3(CENP-A in human), which mostly exists in centromeric nucleosomes, is a universal active centromere mark in eukaryotes and plays an essential role in centromere identity determination. The relationship between centromeric DNA sequences and centromere identity determination is one of the intriguing questions in studying centromere formation. Due to the discoveries in the past decades, including "neocentromeres" and "centromere inactivation", it is now believed that the centromere identity is determined by epigenetic mechanisms. This review will present recent progress in plant centromere biology.展开更多
In order to explore the possible mechanism of corticofugal modulation of excitatory frequency tuning curves (EFTCs) of midbrain neurons, we examined the change of sharpness, frequency-intensity response area, minimum ...In order to explore the possible mechanism of corticofugal modulation of excitatory frequency tuning curves (EFTCs) of midbrain neurons, we examined the change of sharpness, frequency-intensity response area, minimum threshold of both EFTCs and inhibitory frequency tuning curves (IFTCs) of inferior collicular neurons during corticofugal modulation using two-tone inhibition paradigm and micro-electrical stimulation technique. Our data showed that corticofugal inhibition increased sharpness, minimum threshold, and decreased the frequency-intensity response area of EFTCs, at the same time it decreased the sharpness, minimum threshold but increased the frequency-intensity response area of IFTCs. The opposite results were observed for EFTCs and IFTCs of corticofugally facilitated inferior collicular neurons. During corticofugal inhibition, the percent change of frequency-intensity response area of EFTCs had significant correlation with the percent change of that of IFTCs. These data suggest that cortical展开更多
The discharge patterns of neurons in auditory centers encode information about sounds.However,few studies have focused on the synaptic mechanisms underlying the shaping of discharge patterns using intracellular record...The discharge patterns of neurons in auditory centers encode information about sounds.However,few studies have focused on the synaptic mechanisms underlying the shaping of discharge patterns using intracellular recording techniques.Here,we investigated the discharge patterns of inferior collicular（IC）neurons using intracellular recordings to further elucidate the mechanisms underlying the shaping of discharge patterns.Under in vivo intracellular recording conditions,recordings were obtained from 66 IC neurons in 18 healthy adult mice（Mus musculus,Km）under free field-stimulation.Fiftyeight of these neurons fired bursts of action potentials（APs）to auditory stimuli and the remaining eight just generated local responses such as excitatory（n=4）or inhibitory（n=4）postsynaptic potentials.Based on the APs and subthreshold responses,the discharge patterns were classified into seven types：phasic（24/58,41.4%）,phasic burst（8/58,13.8%）,pauser（4/58,6.9%）,phasic-pauser（1/58,1.7%）,chopper（2/58,3.4%）,primary-like tonic（14/58,24.1%）and sound-induced inhibitory（5/58,8.6%）.We concluded that（1）IC neurons exhibit at least seven distinct discharge patterns;（2）inhibition participates in shaping the discharge pattern of most IC neurons and plays a role in sculpting the pattern,except for the primary-like tonic pattern which was not shapedby inhibition;and（3）local neural circuits are the likely structural basis that shapes the discharge patterns of IC neurons and can be formed either in the IC or in lower-level auditory structures.展开更多
The centromere is an essential chromosome site at which the kinetochore forms and loads proteins needed for faithful segregation during the cell cycle and meiosis（Houben et al., 1999;Cleveland et al.,2003;Ma et al.,2...The centromere is an essential chromosome site at which the kinetochore forms and loads proteins needed for faithful segregation during the cell cycle and meiosis（Houben et al., 1999;Cleveland et al.,2003;Ma et al.,2007;Birchler and Han,2009）.Centromere specific sequences such as tandem repeats or transposable elements evolve quickly both within and between the species but have conserved kinetochore proteins（Henikoff and Furuyama,2010）.展开更多
The centromere is a highly organized structure mainly composed of repeat sequences,which make this region extremely difficult for sequencing and other analyses.It plays a conserved role in equal division of chromosome...The centromere is a highly organized structure mainly composed of repeat sequences,which make this region extremely difficult for sequencing and other analyses.It plays a conserved role in equal division of chromosomes into daughter cells in both mitosis and meiosis.However,centromere sequences show notable plasticity.In a dicentric chromosome,one of the centromeres can become inactivated with the underlying DNA unchanged.Furthermore,formerly inactive centromeres can regain activity under certain conditions.In addition,neocentromeres without centromeric repeats have been found in a wide spectrum of species.This evidence indicates that epigenetic mechanisms together with centromeric sequences are associated with centromere specification.展开更多
文摘The centromere, which is one of the essential parts of a chromosome, controls kinetochore formation and chromosome segregation during mitosis and meiosis. While centromere function is conserved in eukaryotes, the centromeric DNA sequences evolve rapidly and have few similarities among species. The histone H3 variant CENH3(CENP-A in human), which mostly exists in centromeric nucleosomes, is a universal active centromere mark in eukaryotes and plays an essential role in centromere identity determination. The relationship between centromeric DNA sequences and centromere identity determination is one of the intriguing questions in studying centromere formation. Due to the discoveries in the past decades, including "neocentromeres" and "centromere inactivation", it is now believed that the centromere identity is determined by epigenetic mechanisms. This review will present recent progress in plant centromere biology.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 39870246) and the research fund from the National Science Foundation of USA (Grant No. NSF IBN 9604238).
文摘In order to explore the possible mechanism of corticofugal modulation of excitatory frequency tuning curves (EFTCs) of midbrain neurons, we examined the change of sharpness, frequency-intensity response area, minimum threshold of both EFTCs and inhibitory frequency tuning curves (IFTCs) of inferior collicular neurons during corticofugal modulation using two-tone inhibition paradigm and micro-electrical stimulation technique. Our data showed that corticofugal inhibition increased sharpness, minimum threshold, and decreased the frequency-intensity response area of EFTCs, at the same time it decreased the sharpness, minimum threshold but increased the frequency-intensity response area of IFTCs. The opposite results were observed for EFTCs and IFTCs of corticofugally facilitated inferior collicular neurons. During corticofugal inhibition, the percent change of frequency-intensity response area of EFTCs had significant correlation with the percent change of that of IFTCs. These data suggest that cortical
基金supported by grants from the National Natural Science Foundation of China (31070971,31000959)
文摘The discharge patterns of neurons in auditory centers encode information about sounds.However,few studies have focused on the synaptic mechanisms underlying the shaping of discharge patterns using intracellular recording techniques.Here,we investigated the discharge patterns of inferior collicular（IC）neurons using intracellular recordings to further elucidate the mechanisms underlying the shaping of discharge patterns.Under in vivo intracellular recording conditions,recordings were obtained from 66 IC neurons in 18 healthy adult mice（Mus musculus,Km）under free field-stimulation.Fiftyeight of these neurons fired bursts of action potentials（APs）to auditory stimuli and the remaining eight just generated local responses such as excitatory（n=4）or inhibitory（n=4）postsynaptic potentials.Based on the APs and subthreshold responses,the discharge patterns were classified into seven types：phasic（24/58,41.4%）,phasic burst（8/58,13.8%）,pauser（4/58,6.9%）,phasic-pauser（1/58,1.7%）,chopper（2/58,3.4%）,primary-like tonic（14/58,24.1%）and sound-induced inhibitory（5/58,8.6%）.We concluded that（1）IC neurons exhibit at least seven distinct discharge patterns;（2）inhibition participates in shaping the discharge pattern of most IC neurons and plays a role in sculpting the pattern,except for the primary-like tonic pattern which was not shapedby inhibition;and（3）local neural circuits are the likely structural basis that shapes the discharge patterns of IC neurons and can be formed either in the IC or in lower-level auditory structures.
文摘The centromere is an essential chromosome site at which the kinetochore forms and loads proteins needed for faithful segregation during the cell cycle and meiosis（Houben et al., 1999;Cleveland et al.,2003;Ma et al.,2007;Birchler and Han,2009）.Centromere specific sequences such as tandem repeats or transposable elements evolve quickly both within and between the species but have conserved kinetochore proteins（Henikoff and Furuyama,2010）.
基金supported by the National Natural Science Foundation of China(Grant No.31071083)National Science Foundation(No.DBI0922703).
文摘The centromere is a highly organized structure mainly composed of repeat sequences,which make this region extremely difficult for sequencing and other analyses.It plays a conserved role in equal division of chromosomes into daughter cells in both mitosis and meiosis.However,centromere sequences show notable plasticity.In a dicentric chromosome,one of the centromeres can become inactivated with the underlying DNA unchanged.Furthermore,formerly inactive centromeres can regain activity under certain conditions.In addition,neocentromeres without centromeric repeats have been found in a wide spectrum of species.This evidence indicates that epigenetic mechanisms together with centromeric sequences are associated with centromere specification.
