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Background: Caudal fin symmetry characterizes teleosts and likely contributes to their evolutionary success. However, the coordinated development and patterning of skeletal elements establishing external symmetry remains incompletely understood. We explore the spatiotemporal emergence of caudal skeletal elements in zebrafish to consider evolutionary and developmental origins of caudal fin symmetry., Results: Transgenic reporters and skeletal staining reveal that the hypural diastema-defining gap between hypurals 2 and 3 forms early and separates progenitors of two plates of connective tissue. Two sets of central principal rays (CPRs) synchronously, sequentially, and symmetrically emerge around the diastema. The two dorsal- and ventral-most rays (peripheral principal rays, PPRs) arise independently and earlier than adjacent CPRs. Muscle and tendon markers reveal that different muscles attach to CPR and PPR sets., Conclusions: We propose that caudal fin symmetry originates from a central organizer that establishes the hypural diastema and bidirectionally patterns surrounding tissue into two plates of connective tissue and two mirrored sets of CPRs. Further, two peripheral organizers unidirectionally specify PPRs, forming a symmetric "composite" fin derived from three fields. Distinct CPR and PPR ontogenies may represent developmental modules conferring ray identities, muscle connections, and biomechanical properties. Our model contextualizes mechanistic studies of teleost fin morphological variation., (© 2022 American Association for Anatomy.)

The RPL44' gene from Saccharomyces cerevisiae encoding the ribosomal protein YP1 beta(L44') has been found to be linked to the STF1 gene, encoding a stabilizing factor of the F1F0-ATPase inhibitor protein from mitochondria. Evidence of this linkage comes from results obtained from Northern hybridization using a DNA probe that contains a complementary region to the 5' end of the mRNA of RPL44'. Similarly, a data bank search has shown that RPL44, encoding ribosomal protein YP2 alpha (L44) is linked to the rig gene that encodes ribosomal protein S21.