scholarly journals longfin causes cis-ectopic expression of the kcnh2a ether-a-go-go K+ channel to autonomously prolong fin outgrowth

2019 ◽  
Author(s):  
Scott Stewart ◽  
Heather K. Le Bleu ◽  
Gabriel A. Yette ◽  
Astra L. Henner ◽  
Amy E. Robbins ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Positional Information ◽  
K Channel ◽  
Chromosome 2 ◽  
Fin Regeneration ◽  
Shape Characteristic ◽  
Small Molecule Inhibition ◽  
Maximal Growth Rate ◽  
Fish Fins ◽  
In Cis

ABSTRACTOrgans stop growing to achieve the size and shape characteristic of the species and in scale with the animal’s body. Likewise, regenerating organs sense injury extents to instruct appropriate replacement growth. Fish fins exemplify both phenomena through their tremendous diversity of form and remarkably robust regeneration. The classic zebrafish mutant longfin develops and regenerates dramatically elongated fins and underlying bony ray skeleton. Here, we show longfin mutant chromosome 2 overexpresses kcnh2a, a voltage-gated potassium channel related to human ether-a-go-go. Genetic disruption of kcnh2a in cis rescues the dominant longfin eponymous phenotype, indicating longfin is a regulatory allele of kcnh2a. We find regenerative fin overgrowth in longfin is characterized by a prolonged outgrowth period rather than increased maximal growth rate. Accordingly, small molecule inhibition of Kcnh2a during late but not early stages of fin regeneration fully suppresses longfin fin overgrowth. Blastula stage transplantations show longfin-expressed kcnh2a acts tissue autonomously in the fin intra-ray mesenchymal lineage, where it is concordantly ectopically expressed. We use temporal delivery of FK506 to show the Ca2+-dependent phosphatase calcineurin likewise entirely acts late in regeneration to attenuate the fin outgrowth period. Epistasis experiments suggest longfin-expressed Kcnh2a inhibits calcineurin signaling to supersede endogenous growth cessation signals. Our results indicate how ion signaling within a growth-determining mesenchyme-lineage controls fin size and morphological variation by tuning outgrowth periods rather than altering positional information.

scholarly journals longfin causes cis-ectopic expression of the kcnh2a ether-a-go-go K+ channel to autonomously prolong fin outgrowth

Development ◽  
2021 ◽  
Author(s):  
Scott Stewart ◽  
Heather K. Le Bleu ◽  
Gabriel A. Yette ◽  
Astra L. Henner ◽  
Amy E. Robbins ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Positional Information ◽  
Characteristic Size ◽  
K Channel ◽  
Chromosome 2 ◽  
Cell Level ◽  
Chemical Inhibition ◽  
Fish Fins ◽  
In Cis ◽  
Temporal Inhibition

Organs stop growing to achieve a characteristic size and shape in scale with the animal's body. Likewise, regenerating organs sense injury extents to instruct appropriate replacement growth. Fish fins exemplify both phenomena through their tremendous diversity of form and remarkably robust regeneration. The classic zebrafish mutant longfint2 develops and regenerates dramatically elongated fins and underlying ray skeleton. We show longfint2 chromosome 2 overexpresses the ether-a-go-go-related voltage-gated potassium channel kcnh2a. Genetic disruption of kcnh2a in cis rescues longfint2, indicating longfint2 is a regulatory kcnh2a allele. We find longfint2 fin overgrowth originates from prolonged outgrowth periods including by showing Kcnh2a chemical inhibition during late stage regeneration fully suppresses overgrowth. Cell transplantations demonstrate longfint2-ectopic kcnh2a acts tissue autonomously within the fin intra-ray mesenchymal lineage. Temporal inhibition of the Ca2+-dependent phosphatase calcineurin indicates it likewise entirely acts late in regeneration to attenuate fin outgrowth. Epistasis experiments suggest longfint2-expressed Kcnh2a inhibits calcineurin output to supersede growth cessation signals. We conclude ion signaling within the growth-determining mesenchyme lineage controls fin size by tuning outgrowth periods rather than altering positional information or cell-level growth potency.

scholarly journals Skeletal geometry and niche transitions restore organ size and shape during zebrafish fin regeneration

2019 ◽  
Author(s):  
Scott Stewart ◽  
Gabriel A. Yette ◽  
Heather K. Le Bleu ◽  
Astra L. Henner ◽  
Joshua A. Braunstein ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Positional Information ◽  
State Transitions ◽  
Injury Site ◽  
Fin Regeneration ◽  
Size And Shape ◽  
Fin Rays ◽  
Fish Fins ◽  
Original Size ◽  
Skeletal Geometry

ABSTRACTRegenerating fish fins return to their original size and shape regardless of the nature or extent of injury. Prevailing models for this longstanding mystery of appendage regeneration speculate fin cells maintain uncharacterized positional identities that instruct outgrowth after injury. Using zebrafish, we find differential Wnt production correlates with the extent of regeneration across the caudal fin. We identify Dachshund transcription factors as markers of distal blastema cells that produce Wnt and thereby promote a pro-progenitor and -proliferation environment. We show these Dach-expressing “niche cells” derive from mesenchyme populating cylindrical and progressively tapered fin rays. The niche pool, and consequently Wnt, steadily dissipates as regeneration proceeds; once exhausted, ray and fin growth stops. Supported by mathematical modeling, we show longfint2 zebrafish regenerate exceptionally long fins due to a perdurant niche, representing a “broken countdown timer”. We propose regenerated fin size is dictated by the amount of niche formed upon damage, which simply depends on the availability of intra-ray mesenchyme defined by skeletal girth at the injury site. Likewise, the fin reestablishes a tapered ray skeleton because progenitor osteoblast output reflects diminishing niche size. This “transpositional scaling” model contends mesenchyme-niche state transitions and positional information provided by self-restoring skeletal geometry rather than cell memories determine a regenerated fin’s size and shape.

scholarly journals An unusual genomic position effect on Drosophila white gene expression: pairing dependence, interactions with zeste, and molecular analysis of revertants.

Genetics ◽  
1992 ◽  
Vol 130 (1) ◽  
pp. 125-138 ◽  
Author(s):  
T Hazelrigg ◽  
S Petersen
Keyword(s):  
Gene Expression ◽  
Regulatory Element ◽  
Position Effect ◽  
Insertion Site ◽  
White Gene ◽  
Chromosome 2 ◽  
Wild Type ◽  
Gene Copies ◽  
In Trans ◽  
In Cis

Abstract The white gene in the AR4-24 P[white,rosy] insertion on chromosome 2 has a novel expression pattern, in which it is repressed in the dorsal half of the eye. X-ray mutagenesis led to the isolation of six revertants mapping to chromosome 2, which are wild type in a zeste+ background, and three extreme derivatives, in which white gene expression is repressed in ventral regions of the eye as well. By Southern blot analyses the breakpoints of five of the revertants and one of the extreme derivatives were mapped in the flanking DNA bordering each side of the AR4-24 insertion. The revertants show some dorsal repression of white in the presence of z1, and by this criterion each is only a partial revertant. The extreme derivatives act not only in cis, but also in trans to repress expression of AR4-24 and its various derivatives. We provide evidence that these trans effects are proximity-dependent effects, possibly mediated by pairing of gene copies, as they do not extend to copies of the white gene located elsewhere in the genome. We show that one extreme derivative, E1, is a small deletion spanning the insertion site at the 5' end of the white gene, and propose that the distance between a negative regulatory element in the 5' flanking DNA and the white promoter influences the degree of the repression.

Transducing positional information to the Hox genes: critical interaction of cdx gene products with position-sensitive regulatory elements

Development ◽  
1998 ◽  
Vol 125 (22) ◽  
pp. 4349-4358 ◽  
Author(s):  
J. Charite ◽  
W. de Graaff ◽  
D. Consten ◽  
M.J. Reijnen ◽  
J. Korving ◽  
...  
Keyword(s):  
Binding Sites ◽  
Hox Genes ◽  
Regulatory Element ◽  
Ectopic Expression ◽  
Positional Information ◽  
Regulatory Elements ◽  
Gene Products ◽  
Anteroposterior Patterning

Studies of pattern formation in the vertebrate central nervous system indicate that anteroposterior positional information is generated in the embryo by signalling gradients of an as yet unknown nature. We searched for transcription factors that transduce this information to the Hox genes. Based on the assumption that the activity levels of such factors might vary with position along the anteroposterior axis, we devised an in vivo assay to detect responsiveness of cis-acting sequences to such differentially active factors. We used this assay to analyze a Hoxb8 regulatory element, and detected the most pronounced response in a short stretch of DNA containing a cluster of potential CDX binding sites. We show that differentially expressed DNA binding proteins are present in gastrulating embryos that bind to these sites in vitro, that cdx gene products are among these, and that binding site mutations that abolish binding of these proteins completely destroy the ability of the regulatory element to drive regionally restricted expression in the embryo. Finally, we show that ectopic expression of cdx gene products anteriorizes expression of reporter transgenes driven by this regulatory element, as well as that of the endogenous Hoxb8 gene, in a manner that is consistent with them being essential transducers of positional information. These data suggest that, in contrast to Drosophila Caudal, vertebrate cdx gene products transduce positional information directly to the Hox genes, acting through CDX binding sites in their enhancers. This may represent the ancestral mode of action of caudal homologues, which are involved in anteroposterior patterning in organisms with widely divergent body plans and modes of development.

scholarly journals THE GENETIC SYSTEM CONTROLLING RECOMBINATION IN THE SILKWORM

Genetics ◽  
1981 ◽  
Vol 99 (2) ◽  
pp. 231-245
Author(s):  
Hiroyasu Ebinuma ◽  
Narumi Yoshitake
Keyword(s):  
Chromosomal Aberrations ◽  
Recombination Frequency ◽  
Genetic System ◽  
Chromosome 2 ◽  
Chromosome 5 ◽  
Recombination Rates ◽  
Heterozygous Condition ◽  
In Trans ◽  
The Mean ◽  
In Cis

ABSTRACT The nature of recombination modifiers was investigated in Bombyx mori lines selected for high (H) and low (L) recombination rates between the pS and Y loci in chromosome 2. Since the mean recombination rates for the H × L and L × H F1 crosses were approximately intermediate between those of high and low lines, the cytoplasmic maternal effect and difference in the activity of recombination modifiers between marked and unmarked second chromosomes were not detected. The H × (L × H), H × (H × L), L × (L × H) and L × (H × L) backcrosses indicated the presence of additive and dominance effects of marked and unmarked second chromosomes and the remaining chromosomes.——Recombination rates between the pS and Y loci in chromosome 2 and half-nonrecombination rates between the pe and re loci in chromosome 5 of high and low lines indicated that these recombination modifiers caused changes in the recombination frequency between pS and Y in chromosome 2, but not between pe and re in chromosome 5.——There were no differences in viability between individuals having the second chromosomes of the recombinant types [pS +, pY (H); pS +, + Y (L)] and those of the nonrecombinant types [pS Y, p + (H); pS Y, + + (L)] in both high and low lines. Mean recombination rates measured in cis [pS Y/p + (H); pS Y/+ + (L)] and trans [pS +/p Y (H); pS +/+ Y (L)] males were the same in the high but not in the low line. No segregation of a single recombination modifier was indicated by the distribution of recombination rates measured in trans males [pS +/p Y (H); pS +/+ Y (L)] of high and low lines. Accordingly, the recombination modifiers distributed on chromosome 2 in the heterozygous condition were not gross chromosomal aberrations, but polygenic factors in the low line.

scholarly journals Transvection in the Drosophila Ultrabithorax gene: a Cbx1 mutant allele induces ectopic expression of a normal allele in trans.

Genetics ◽  
1990 ◽  
Vol 126 (1) ◽  
pp. 177-184 ◽  
Author(s):  
J E Castelli-Gair ◽  
J L Micol ◽  
A García-Bellido
Keyword(s):  
Double Mutant ◽  
Ectopic Expression ◽  
Imaginal Discs ◽  
Wing Disc ◽  
Loss Of Function ◽  
Normal Allele ◽  
Single Mutant ◽  
Adult Wing ◽  
Disc Cells ◽  
In Cis

Abstract In wild-type Drosophila melanogaster larvae, the Ultrabithorax (Ubx) gene is expressed in the haltere imaginal discs but not in the majority of cells of the wing imaginal discs. Ectopic expression of the Ubx gene in wing discs can be elicited by the presence of Contrabithorax (Cbx) gain-of-function alleles of the Ubx gene or by loss-of-function mutations in Polycomb (Pc) or in other trans-regulatory genes which behave as repressors of Ubx gene activity. Several Ubx loss-of-function alleles cause the absence of detectable Ubx proteins (UBX) or the presence of truncated UBX lacking the homeodomain. We have compared adult wing phenotypes with larval wing disc UBX patterns in genotypes involving double mutant chromosomes carrying in cis one of those Ubx mutations and the Cbx1 mutation. We show that such double mutant genes are (1) active in the same cells in which the single mutant Cbx1 is expressed, although they are unable to yield functional proteins, and (2) able to induce ectopic expression of a normal homologous Ubx allele in a part of the cells in which the single mutant Cbx1 is active. That induction is conditional upon pairing of the homologous chromosomes (the phenomenon known as transvection), and it is not mediated by UBX. Depletion of Pc gene products by Pc3 mutation strongly enhances the induction phenomenon, as shown by (1) the increase of the number of wing disc cells in which induction of the homologous allele is detectable, and (2) the induction of not only a paired normal allele but also an unpaired one.

scholarly journals spiel ohne grenzen/pou2is required during establishment of the zebrafish midbrain-hindbrain boundary organizer

Development ◽  
2001 ◽  
Vol 128 (21) ◽  
pp. 4165-4176 ◽  
Author(s):  
Heinz-Georg Belting ◽  
Giselbert Hauptmann ◽  
Dirk Meyer ◽  
Salim Abdelilah-Seyfried ◽  
Ajay Chitnis ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Ectopic Expression ◽  
Regional Identity ◽  
Positional Information ◽  
Neural Plate ◽  
Pou Domain ◽  
Normal Expression ◽  
Organizing Center ◽  
Wnt1 Expression ◽  
Permissive Role

The vertebrate midbrain-hindbrain boundary (MHB) organizes patterning and neuronal differentiation in the midbrain and anterior hindbrain. Formation of this organizing center involves multiple steps, including positioning of the MHB within the neural plate, establishment of the organizer and maintenance of its regional identity and signaling activities. Juxtaposition of the Otx2 and Gbx2 expression domains positions the MHB. How the positional information is translated into activation of Pax2, Wnt1 and Fgf8 expression during MHB establishment remains unclear. In zebrafish spiel ohne grenzen (spg) mutants, the MHB is not established, neither isthmus nor cerebellum form, the midbrain is reduced in size and patterning abnormalities develop within the hindbrain. In spg mutants, despite apparently normal expression of otx2, gbx1 and fgf8 during late gastrula stages, the initial expression of pax2.1, wnt1 and eng2, as well as later expression of fgf8 in the MHB primordium are reduced. We show that spg mutants have lesions in pou2, which encodes a POU-domain transcription factor. Maternal pou2 transcripts are distributed evenly in the blastula, and zygotic expression domains include the midbrain and hindbrain primordia during late gastrulation. Microinjection of pou2 mRNA can rescue pax2.1 and wnt1 expression in the MHB of spg/pou2 mutants without inducing ectopic expression. This indicates an essential but permissive role for pou2 during MHB establishment. pou2 is expressed normally in noi/pax2.1 and ace/fgf8 zebrafish mutants, which also form no MHB. Thus, expression of pou2 does not depend on fgf8 and pax2.1. Our data suggest that pou2 is required for the establishment of the normal expression domains of wnt1 and pax2.1 in the MHB primordium.

The Hox gene Abdominal-B antagonizes appendage development in the genital disc of Drosophila

Development ◽  
2001 ◽  
Vol 128 (3) ◽  
pp. 331-339 ◽  
Author(s):  
B. Estrada ◽  
E. Sanchez-Herrero
Keyword(s):  
Ectopic Expression ◽  
Posterior Part ◽  
Positional Information ◽  
The Body ◽  
Wild Type ◽  
Male And Female ◽  
Hox Gene ◽  
Appendage Development ◽  
Genital Disc ◽  
Expression Of Genes

In Drosophila, the Hox gene Abdominal-B is required to specify the posterior abdomen and the genitalia. Homologues of Abdominal-B in other species are also needed to determine the posterior part of the body. We have studied the function of Abdominal-B in the formation of Drosophila genitalia, and show here that absence of Abdominal-B in the genital disc of Drosophila transforms male and female genitalia into leg or, less frequently, into antenna. These transformations are accompanied by the ectopic expression of genes such as Distal-less or dachshund, which are normally required in these appendages. The extent of wild-type and ectopic Distal-less expression depends on the antagonistic activities of the Abdominal-B gene, as a repressor, and of the decapentaplegic and wingless genes as activators. Absence of Abdominal-B also changes the expression of Homothorax, a Hox gene co-factor. Our results suggest that Abdominal-B forms genitalia by modifying an underlying positional information and repressing appendage development. We propose that the genital primordia should be subdivided into two regions, one of them competent to be transformed into an appendage in the absence of Abdominal-B.

Involvement of the sonic hedgehog, patched 1 and bmp2 genes in patterning of the zebrafish dermal fin rays

Development ◽  
1998 ◽  
Vol 125 (21) ◽  
pp. 4175-4184 ◽  
Author(s):  
L. Laforest ◽  
C.W. Brown ◽  
G. Poleo ◽  
J. Geraudie ◽  
M. Tada ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Sonic Hedgehog ◽  
Bone Matrix ◽  
Basal Layer ◽  
Pectoral Fin ◽  
Expression Domain ◽  
Fin Regeneration ◽  
Fin Rays ◽  
Dermal Bone ◽  
Fish Fins

The signaling molecule encoded by Sonic hedgehog (shh) participates in the patterning of several embryonic structures including limbs. During early fin development in zebrafish, a subset of cells in the posterior margin of pectoral fin buds express shh. We have shown that regulation of shh in pectoral fin buds is consistent with a role in mediating the activity of a structure analogous to the zone of polarizing activity (ZPA) (Akimenko and Ekker (1995) Dev. Biol. 170, 243–247). During growth of the bony rays of both paired and unpaired fins, and during fin regeneration, there does not seem to be a region equivalent to the ZPA and one would predict that shh would play a different role, if any, during these processes specific to fish fins. We have examined the expression of shh in the developing fins of 4-week old larvae and in regenerating fins of adults. A subset of cells in the basal layer of the epidermis in close proximity to the newly formed dermal bone structures of the fin rays, the lepidotrichia, express shh, and ptc1 which is thought to encode the receptor of the SHH signal. The expression domain of ptc1 is broader than that of shh and adjacent blastemal cells releasing the dermal bone matrix also express ptc1. Further observations indicate that the bmp2 gene, in addition to being expressed in the same cells of the basal layer of the epidermis as shh, is also expressed in a subset of the ptc1-expressing cells of the blastema. Amputations of caudal fins immediately after the first branching point of the lepidotrichia, and global administration of all-trans-retinoic acid, two procedures known to cause fusion of adjacent rays, result in a transient decrease in the expression of shh, ptc1 and bmp2. The effects of retinoic acid on shh expression occur within minutes after the onset of treatment suggesting direct regulation of shh by retinoic acid. These observations suggest a role for shh, ptc1 and bmp2 in patterning of the dermoskeleton of developing and regenerating teleost fins.

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