Pentadactyl limbs represent a conserved morphological feature among tetrapods,with anterior digits considered more important than posterior digits for refined movement.While posterior digit formation is governed by gr...Pentadactyl limbs represent a conserved morphological feature among tetrapods,with anterior digits considered more important than posterior digits for refined movement.While posterior digit formation is governed by graded expression of the Shh and 5’Hox genes,the regulatory mechanisms underlying anterior digit development,especially digit I(DI),remain poorly defined.This study identified an anterior expression pattern of Zic3 in the limb buds of representative tetrapods,including humans,which exerted an inhibitory effect on skeletal development.Zic3 was highly expressed in the anterior region of limb buds at early developmental stages,with species-specific divergence emerging during later development.Overexpression of Zic3 significantly delayed chondrogenesis and ossification,leading to bone shortening but not loss.Furthermore,RNA sequencing demonstrated that Zic3 down-regulated key genes associated with skeletal development,including Cytl1,Sox9,Ihh,Ptch1,Runx2,and Wnt16.These findings demonstrate that Zic3 acts as a conserved inhibitor of anterior skeletal maturation and contributes to the molecular asymmetry of tetrapod limb development.展开更多
Morphological changes during the embryonic development of limbs of the green turtle,Chelonia mydas,were studied during the entire period of incubation,using transmission and scanning electron microscopy(TEM and SEM). ...Morphological changes during the embryonic development of limbs of the green turtle,Chelonia mydas,were studied during the entire period of incubation,using transmission and scanning electron microscopy(TEM and SEM). Limb buds were first observed at Stage 2. At that stage,the tip was covered with an apical ectodermal ridge(AER) which began to regress at Stage 6. Associated with AER was the presence of the mesenchymal cells which,consequently,differentiated into muscles,cartilage and bones. The gross features of the skeletal development appeared as a condensation of the cartilaginous structures in the proximal distal region of the limbs. The primordial digits were gradually enclosed by hard keratinized webbed skin. The increase in rate of ossification and skin pigmentation was correlated with the growth of the limbs. The development of the limbs was closely related to the transitional appearance of mucus secretion from the epidermis.展开更多
Understanding limb development not only gives insights into the outgrowth and differentiation of the limb,but also has clinical relevance.Limb development begins with two paired limb buds(forelimb and hindlimb buds),w...Understanding limb development not only gives insights into the outgrowth and differentiation of the limb,but also has clinical relevance.Limb development begins with two paired limb buds(forelimb and hindlimb buds),which are initially undifferentiated mesenchymal cells tipped with a thickening of the ectoderm,termed the apical ectodermal ridge(AER).As a transitional embryonic structure,the AER undergoes four stages and contributes to multiple axes of limb development through the coordination of signalling centres,feedback loops,and other cell ac-tivities by secretory signalling and the activation of gene expression.Within the scope of proximodistal pattering,it is understood that while fibroblast growth factors(FGFs)function sequentially over time as primary components of the AER signalling process,there is still no consensus on models that would explain proximodistal patterning itself.In anteroposterior pattermning,the AER has a dual-direction regulation by which it promotes the sonic hedgehog(Shh)gene expression in the zone of polarizing activity(ZPA)for proliferation,and inhibits Shh expression in the anterior mesenchyme.In dorsoventral patterming,the AER activates Engrailed-1(En1)expression,and thus represses Wnt family member 7a(Wnt7a)expression in the ventral ectoderm by the expression of Fgfs,Sp6/8,and bone morpho-genetic protein(Bmp)genes.The AER also plays a vital role in shaping the individual digits,since levels of Fgf4/8 and Bmps expressed in the AER affect digit patterning by controlling apoptosis.In summary,the knowledge of crosstalk within AER among the three main axes is essential to understand limb growth and pattern fomation,as the development of its areas proceeds simultaneously.展开更多
The insect limb develops from the imaginal disc or larval leg during metamor- phosis. The molecular mechanisms involved in the development from the larval to the adult leg are poorly understood. Herein, we cloned the ...The insect limb develops from the imaginal disc or larval leg during metamor- phosis. The molecular mechanisms involved in the development from the larval to the adult leg are poorly understood. Herein, we cloned the full length of a zinc finger gene rotund from Bombyx mori （Bmrn）, which contained a 1419 bp open reading frame, and encoded a 473 amino acid protein. Reverse transcription polymerase chain reaction and Western blot analyses demonstrated that Bmrn was expressed at higher levels in the epidermis than in other tissues tested, and it showed a very high expression level during metamorphosis. Knock-down of Bmrn produced defects in the tarsus and pretarsus, including the fusion and reduction of tarsomeres, and the developmental arrest of pretarsus. Our data showed that Bmrn is involved in the formation of the tarsus and pretarsus, whereas its homologous gene in Drosophila has been shown to affect three tarsal segments （t2-t4）, suggesting that the remodeling of the leg has involved changes in the patterning of gene regulation during evolution.展开更多
Limb loss shows recurrent phenotypic evolution across squamate lineages.Here,based on three de novo-assembled genomes of limbless lizards from different lineages,we showed that divergence of conserved non-coding eleme...Limb loss shows recurrent phenotypic evolution across squamate lineages.Here,based on three de novo-assembled genomes of limbless lizards from different lineages,we showed that divergence of conserved non-coding elements(CNEs)played an important role in limb development.These CNEs were associated with genes required for limb initiation and outgrowth,and with regulatory signals in the early stage of limb development.Importantly,we identified the extensive existence of insertions and deletions(In Dels)in the CNEs,with the numbers ranging from 111 to 756.Most of these CNEs with In Dels were lineagespecific in the limbless squamates.Nearby genes of these In Del CNEs were important to early limb formation,such as Tbx4,Fgf10,and Gli3.Based on functional experiments,we found that nucleotide mutations and In Dels both affected the regulatory function of the CNEs.Our study provides molecular evidence underlying limb loss in squamate reptiles from a developmental perspective and sheds light on the importance of regulatory element In Dels in phenotypic evolution.展开更多
The overlapping roles of Hippo and Hedgehog signaling in biological functions and diseases prompt us to inves-tigate their potential interactions.Activation of Hippo signaling enhances the transcriptional output of He...The overlapping roles of Hippo and Hedgehog signaling in biological functions and diseases prompt us to inves-tigate their potential interactions.Activation of Hippo signaling enhances the transcriptional output of Hedgehog signaling,and the role of Hippo signaling in regulating Hedgehog signaling relies on the Hippo pathway key effector,Taz.Interestingly,Taz exhibits a gradient expression across the posterior-to-anterior of limb bud mesoderms,similar to Sonic hedgehog(Shh).Importantly,Taz drives PKA to phosphorylate Gli3,resulting in the Gli3 processing into its repressor and attenuation of Hedgehog signaling in the Shh-independent manner.Specifically,Taz deletion in mouse embryonic limb bud mesenchyme not only enhances the Hedgehog signaling but partially restores the phenotypes from Shh deletion in causing severe defects of anteroposterior patterning and digit number and identity.Together,these results uncover Taz-dependent Gli3 processing as a hitherto uncharacterized mechanism controlling Hedgehog signaling,highlighting its cross-regulation by Hippo signaling.展开更多
基金supported by the Department of Science&Technology of Liaoning Province(2024-MS-099,2024-BS-093)。
文摘Pentadactyl limbs represent a conserved morphological feature among tetrapods,with anterior digits considered more important than posterior digits for refined movement.While posterior digit formation is governed by graded expression of the Shh and 5’Hox genes,the regulatory mechanisms underlying anterior digit development,especially digit I(DI),remain poorly defined.This study identified an anterior expression pattern of Zic3 in the limb buds of representative tetrapods,including humans,which exerted an inhibitory effect on skeletal development.Zic3 was highly expressed in the anterior region of limb buds at early developmental stages,with species-specific divergence emerging during later development.Overexpression of Zic3 significantly delayed chondrogenesis and ossification,leading to bone shortening but not loss.Furthermore,RNA sequencing demonstrated that Zic3 down-regulated key genes associated with skeletal development,including Cytl1,Sox9,Ihh,Ptch1,Runx2,and Wnt16.These findings demonstrate that Zic3 acts as a conserved inhibitor of anterior skeletal maturation and contributes to the molecular asymmetry of tetrapod limb development.
文摘Morphological changes during the embryonic development of limbs of the green turtle,Chelonia mydas,were studied during the entire period of incubation,using transmission and scanning electron microscopy(TEM and SEM). Limb buds were first observed at Stage 2. At that stage,the tip was covered with an apical ectodermal ridge(AER) which began to regress at Stage 6. Associated with AER was the presence of the mesenchymal cells which,consequently,differentiated into muscles,cartilage and bones. The gross features of the skeletal development appeared as a condensation of the cartilaginous structures in the proximal distal region of the limbs. The primordial digits were gradually enclosed by hard keratinized webbed skin. The increase in rate of ossification and skin pigmentation was correlated with the growth of the limbs. The development of the limbs was closely related to the transitional appearance of mucus secretion from the epidermis.
基金Key Research and Development Project of Shandong Province(No.2017G006043),China。
文摘Understanding limb development not only gives insights into the outgrowth and differentiation of the limb,but also has clinical relevance.Limb development begins with two paired limb buds(forelimb and hindlimb buds),which are initially undifferentiated mesenchymal cells tipped with a thickening of the ectoderm,termed the apical ectodermal ridge(AER).As a transitional embryonic structure,the AER undergoes four stages and contributes to multiple axes of limb development through the coordination of signalling centres,feedback loops,and other cell ac-tivities by secretory signalling and the activation of gene expression.Within the scope of proximodistal pattering,it is understood that while fibroblast growth factors(FGFs)function sequentially over time as primary components of the AER signalling process,there is still no consensus on models that would explain proximodistal patterning itself.In anteroposterior pattermning,the AER has a dual-direction regulation by which it promotes the sonic hedgehog(Shh)gene expression in the zone of polarizing activity(ZPA)for proliferation,and inhibits Shh expression in the anterior mesenchyme.In dorsoventral patterming,the AER activates Engrailed-1(En1)expression,and thus represses Wnt family member 7a(Wnt7a)expression in the ventral ectoderm by the expression of Fgfs,Sp6/8,and bone morpho-genetic protein(Bmp)genes.The AER also plays a vital role in shaping the individual digits,since levels of Fgf4/8 and Bmps expressed in the AER affect digit patterning by controlling apoptosis.In summary,the knowledge of crosstalk within AER among the three main axes is essential to understand limb growth and pattern fomation,as the development of its areas proceeds simultaneously.
基金We are grateful to the following individuals for their helpful comments and reviews during the preparation of this manuscript： Zhao-Ming Dong, Peng-Chao Guo. This work was supported by grants from the State Key Program of the National Natural Science of China （No. 31530071 ） and the National Natural Science Foundation of China （No. 31272502 and No. 30800804）.
文摘The insect limb develops from the imaginal disc or larval leg during metamor- phosis. The molecular mechanisms involved in the development from the larval to the adult leg are poorly understood. Herein, we cloned the full length of a zinc finger gene rotund from Bombyx mori （Bmrn）, which contained a 1419 bp open reading frame, and encoded a 473 amino acid protein. Reverse transcription polymerase chain reaction and Western blot analyses demonstrated that Bmrn was expressed at higher levels in the epidermis than in other tissues tested, and it showed a very high expression level during metamorphosis. Knock-down of Bmrn produced defects in the tarsus and pretarsus, including the fusion and reduction of tarsomeres, and the developmental arrest of pretarsus. Our data showed that Bmrn is involved in the formation of the tarsus and pretarsus, whereas its homologous gene in Drosophila has been shown to affect three tarsal segments （t2-t4）, suggesting that the remodeling of the leg has involved changes in the patterning of gene regulation during evolution.
基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB31000000)the National Natural Science Foundation of China(32220103004,32000296)+2 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0501)the International Partnership Program of Chinese Academy of Sciences(151751KYSB20190024)the Sichuan Science and Technology Program(2021JDJQ0002)。
文摘Limb loss shows recurrent phenotypic evolution across squamate lineages.Here,based on three de novo-assembled genomes of limbless lizards from different lineages,we showed that divergence of conserved non-coding elements(CNEs)played an important role in limb development.These CNEs were associated with genes required for limb initiation and outgrowth,and with regulatory signals in the early stage of limb development.Importantly,we identified the extensive existence of insertions and deletions(In Dels)in the CNEs,with the numbers ranging from 111 to 756.Most of these CNEs with In Dels were lineagespecific in the limbless squamates.Nearby genes of these In Del CNEs were important to early limb formation,such as Tbx4,Fgf10,and Gli3.Based on functional experiments,we found that nucleotide mutations and In Dels both affected the regulatory function of the CNEs.Our study provides molecular evidence underlying limb loss in squamate reptiles from a developmental perspective and sheds light on the importance of regulatory element In Dels in phenotypic evolution.
基金supported by National Basic Research Program of China(No.2018YFC1004404)National Natural Science Foundation of China(Nos.31071292,32170841,31271561,31571493,81741043,31871395,and 31801207).
文摘The overlapping roles of Hippo and Hedgehog signaling in biological functions and diseases prompt us to inves-tigate their potential interactions.Activation of Hippo signaling enhances the transcriptional output of Hedgehog signaling,and the role of Hippo signaling in regulating Hedgehog signaling relies on the Hippo pathway key effector,Taz.Interestingly,Taz exhibits a gradient expression across the posterior-to-anterior of limb bud mesoderms,similar to Sonic hedgehog(Shh).Importantly,Taz drives PKA to phosphorylate Gli3,resulting in the Gli3 processing into its repressor and attenuation of Hedgehog signaling in the Shh-independent manner.Specifically,Taz deletion in mouse embryonic limb bud mesenchyme not only enhances the Hedgehog signaling but partially restores the phenotypes from Shh deletion in causing severe defects of anteroposterior patterning and digit number and identity.Together,these results uncover Taz-dependent Gli3 processing as a hitherto uncharacterized mechanism controlling Hedgehog signaling,highlighting its cross-regulation by Hippo signaling.
