Highlights d Genetic screen identifies a mutation (mem, pola2) that disrupts fin regeneration d pola2 inactivation causes a long-lasting reduction in size of new structures d pola2 inactivation alters blastemal proliferation and size d Progenitor cell-cycle interference alters positional memory in several contexts

No abstract

Two rice cDNA clones pTS1 and pTS3 were screened at reduced stringency from a cDNA library generated from rice seedling poly(A) RNA by a partial cDNA fragment of soybean 17.5E (pCE53). The rice seedlings were induced at 41 ° C for 2 h before harvest for RNA extraction. Both clones were identified by a hybrid-selected in vitro translation assay and proved to belong to the low-molecular-mass heat-shock protein group (16-20 kDa). The rice pTS1 clone has an open reading frame encoding a 150 amino acid residue 16.9kDa protein which is 72.3~o, 75.3~o and 83.7~o identical to soybean HSP 17.5E [1], pea HSP 179a [2] and wheat C5-8 [3], respectively. On the other hand, the pTS3 cDNA clone encodes a 155 amino acid residue 17.3 kDa protein which is 70.9~o, 73.1~o, 67.5~o identical to soybean HSP 17.5E, pea HSP 179a and wheat C5-8, respectively. A series of pairwise sequence comparisons show that the two eDNA clones belong to the class I low-molecular-weight heatshock protein family. Among the members of this family, they share a higher homology at the carboxyl terminal than at the amino terminal, as all HSPs do. Both the cDNA and deduced amino acid sequences of the two clones are shown in Fig. 1 and Fig. 2.

Skin expansion during development is predominantly driven by growth of basal epithelial cell (BEC)-derived clonal populations, which often display varied sizes and shapes. However, little is known about the causes of clonal heterogeneity and the maximum size to which a single clone can grow. Here, we created a zebrafish model, basebow, for capturing clonal growth behavior in the BEC population on a whole-body, centimeter scale. By tracking 222 BECs over the course of a 28-fold expansion of body surface area, we determined that most BECs survive and grow clonal populations with an average size of 0.013 mm2. An extensive survey of 742 sparsely labeled BECs further revealed that giant dominant clones occasionally arise on specific body regions, covering up to 0.6% of the surface area. Additionally, a growth-induced extracellular matrix component, Lamb1a, mediates clonal growth in a cell-autonomous manner. Altogether, our findings demonstrate how clonal heterogeneity and clonal dominance may emerge to enable post-embryonic growth of a vertebrate organ, highlighting key cellular mechanisms that may only become evident when visualizing single cell behavior at the whole animal level.

Wing fok, chiao-ping chen, tzu-Lun tseng, Yi-Hua chiang & Jiun-Hong chen ✉ Although apoptosis has been widely observed during the regenerative process, the mechanisms by which it is regulated and its roles in regeneration remained unclear. in this study, we introduced Aeolosoma viride, a fresh water annelid with an extraordinary regenerative ability as our model organism to study the functions and regulations of apoptotic caspases. Here we showed that major events of apoptosis were detected near the wounded area and showed spatial correlation with the expression patterns of caspase gene namely Avi-caspase X and two apoptosis regulators namely Avi-Bax and Avi-Bcl-xL. next, we investigated how Avi-caspase X gene expression and apoptosis influence regeneration following head amputation. RnA interference of Avi-caspase X reduced the amounts of apoptotic cells, as well as the percentage of successful regeneration, suggesting a critical role for apoptosis in anterior regeneration of A. viride. in addition, we also discovered that the expression of apoptotic caspases was regulated by the canonical Wnt signaling pathway. together, our study showed that caspase dependent apoptosis was critical to the anterior regeneration of A. viride, and could be regulated by the canonical Wnt signaling pathway. Aeolosoma viride is a fresh water annelid that can regenerate both anteriorly and posteriorly within 5 days after amputation 1. Amputation created a rough and uneven wounded area that smoothened around 12 hours post amputation (hpa). After 12 hpa, a hyaline cell masses started to develop at the regenerating area which characterized blastema formation. Mouth formation was initiated around 96 hpa, in which a circular structure reappeared at the ventral side of the peristomium. After 96 hpa, the anterior regenerating head bulged and became wider than posterior segments. Most worms are freely to move at 120 hpa, which was considered as a successful anterior regeneration 2. Previous studies showed that cell proliferation is required for the formation of blastema in A. viride 2. Similar to many animal species, undifferentiated cells from the blastema can proliferate and differentiate in an orderly manner to replace the missing body parts, tissues or organs in this annelid 3-5. Since many multicellular organisms maintain an appropriate body size, cell proliferation must be coordinated with other biological processes. One of such mechanisms is apoptosis 6. Apoptosis is a form of programmed cell death that eliminates cells that are damaged or no longer required in a coordinated manner 7. In many organisms, apoptosis is a normal and essential part of development. Studies have confirmed that apoptosis is necessary for the proper development of many organisms for it affect a wide range of biological processes 8-11. Organs and tissues that are only useful during the embryonic stage are eliminated by apoptosis to allow further development. Coordinated apoptosis on a large group of cells provide a mean to shape interdigital tissue in many vert...