Clock1a affects mesoderm development and primitive hematopoiesis by regulating Nodal-Smad3 signaling in the zebrafish
Sha-Sha Bian1, Xu-Lei Zheng1, Hua-Qin Sun2
1From the Laboratory of Medical Genetics, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University and Collaborative Innovation Center Chengdu 610041, China.
Abstract:
Circadian clock and Smad2/3/4-mediated Nodal signaling regulate multiple physiological and pathological processes. However, it remains unknown whether Clock directly cross-talks with Nodal signaling and how this would regulate embryonic development. Here we show that Clock1a coordinated mesoderm development and primitive hematopoiesis in zebrafish embryos by directly up-regulating Nodal-Smad3 signaling. We found that Clock1a is expressed both maternally and zygotically throughout early zebrafish development. We also noted that Clock1a alterations produce embryonic defects with shortened body length, lack of the ventral tail fin, or partial defect of the eyes. Clock1a regulates the expression of the mesodermal markers ntl, gsc, and eve1 and of the hematopoietic markers scl, lmo2, and fli1a Biochemical analyses revealed that Clock1a stimulates Nodal signaling by increasing expression of Smad2/3/4. Mechanistically, Clock1a activates the smad3a promoter via its E-box1 element (CAGATG). Taken together, these findings provide mechanistic insight into the role of Clock1a in the regulation of mesoderm development and primitive hematopoiesis via modulation of Nodal-Smad3 signaling and indicate that Smad3a is directly controlled by the circadian clock in zebrafish.
Insights
The circadian clock protein Clock1a directly enhances Nodal signaling by up-regulating Smad2/3/4, coordinating mesoderm development and primitive hematopoiesis in zebrafish embryos.
Area of Science:
- Developmental Biology
- Chronobiology
- Molecular Signaling
Background:
- Circadian clocks and Nodal signaling are crucial for development.
- The interaction between Clock proteins and Nodal signaling in embryonic development is not well understood.
Purpose of the Study:
- To investigate the direct cross-talk between Clock1a and Nodal signaling.
- To elucidate the role of this interaction in zebrafish embryonic development.
Main Methods:
- Zebrafish embryo analysis for Clock1a expression and function.
- Mesodermal and hematopoietic marker gene expression analysis.
- Biochemical assays to determine Clock1a's effect on Nodal signaling components and promoter activity.
Main Results:
- Clock1a is expressed maternally and zygotically in early zebrafish embryos.
- Clock1a alterations lead to defects in body length, tail fin, and eye development.
- Clock1a up-regulates mesodermal (ntl, gsc, eve1) and hematopoietic (scl, lmo2, fli1a) markers.
- Clock1a increases Smad2/3/4 expression and directly activates the smad3a promoter via an E-box element.
Conclusions:
- Clock1a coordinates mesoderm development and primitive hematopoiesis in zebrafish.
- Clock1a modulates Nodal-Smad3 signaling pathway.
- Smad3a expression is directly regulated by the circadian clock in zebrafish.
