Dataset Information

PRPS polymerization influences lens fiber organization in zebrafish.

ABSTRACT:

Background

The self-assembly of metabolic enzymes into filaments or foci highlights an intriguing mechanism for the regulation of metabolic activity. Recently, we identified the conserved polymerization of phosphoribosyl pyrophosphate synthetase (PRPS), which catalyzes the first step in purine nucleotide synthesis, in yeast and cultured mammalian cells. While previous work has revealed that loss of PRPS activity regulates retinal development in zebrafish, the extent to which PRPS filament formation affects tissue development remains unknown.

Results

By generating novel alleles in the zebrafish PRPS paralogs, prps1a and prps1b, we gained new insight into the role of PRPS filaments during eye development. We found that mutations in prps1a alone are sufficient to generate abnormally small eyes along with defects in head size, pigmentation, and swim bladder inflation. Furthermore, a loss-of-function mutation that truncates the Prps1a protein resulted in the failure of PRPS filament assembly. Lastly, in mutants that fail to assemble PRPS filaments, we observed disorganization of the actin network in the lens fibers.

Conclusions

The truncation of Prps1a blocked PRPS filament formation and resulted in a disorganized lens fiber actin network. Altogether, these findings highlight a potential role for PRPS filaments during lens fiber organization in zebrafish.

SUBMITTER: Begovich K

PROVIDER: S-EPMC8370018 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The mammalian lens consists of an aged core of quiescent cells enveloped by a layers of mature fully elongated and younger, continuously elongating and transcriptionaly active cells. In the present study, we compared global gene expression profiles in elongating and mature, non-elongating fiber cells. The microarray-based comparison of gene expression profiles was performed using Agilent 22K Mouse Oligo microarrays with two rounds of RNA amplification from samples obtained by laser capture microdissection (LCM) of paraffin-embedded lens sections. Lenses were removed and immediately fixed using 4% paraformaldehide or methanol-based UMFIX reagent (Sakura Finetek USA, Inc.). To map the exact location of both elongating and maturing fibers on the lens slices, lenses were vibratome-sliced (Vibratome 1000, St. Louis, MO) as described previously and the GFP expression pattern was captured by confocal microscopy. For RNA extraction lens tissue was sliced into 5 micron-thick paraffin sections and microdissected using LCM (Leica Microsystems, Bannockburn, IL). The mid-saggital slices were used both for syncytium border measurements and for LCM. Control measurement (data not shown) confirmed that similar rates of shrinkage in paraformaldehyde- and UMFIX-fixed samples did not affect precision of LCM dissection. Fiber cell samples were dissected out of 5 micron-thick slices. In one experiment we typically processed about 40 slices, which was sufficient to collect the minimum of 200 zone-specific cells pooled from P5 littermate lenses. This sample size provided a reliable representation of RNA species in experimental procedure originally designed and tested for just 1-10 cells. Localization of the syncytium border characterized by the abrupt change of GFP labeling pattern was captured by confocal microscopy as described previously. In brief, GFP fluorescence was visualized using LSM510 instrument (Carl Zeiss, NY) equipped with an argon/krypton laser at 488 nm excitation and a 515-565 nm band pass emission filter. Physical parameters of the zones containing young and maturing fibers were measured in fixed lens slices using the morhphometric software provided by Zeiss. Lenses were fixed in 4% paraformaldehyde/PBS and sectioned with a vibratome. Cells from elongating and maturing fiber regions were dissected out using the Leica DMLA laser capture microscope, (Leica Microsystems, Bannockburn, IL). The cut-out pieces containing captured cells were put directly into tubes containing the lysis buffer supplied in the Absolutely RNAÂ® nanoprep kit (Stratagene, La Jolla, CA). Total RNA from the microdissected tissue sections was extracted and purified using the Absolutely RNA nanoprep kit according to the manufacturer's protocol. Caps briefly placed onto the section without laser activation were used as negative controls. Samples from several age-matched lenses were pooled together to obtain differentiation-specific samples for microarray analysis. Target RNA amplification and labeling with Cy-3 or Cy-5 dyes from CyDye Post Labelling Reactive Dye Pack (Amersham, USA) was carried out in two rounds using the Amino Allyl MessageAmpâ?¢ aRNA Kit (Ambion, USA) as specified by the manufacturer. Quality and size distribution of the targets were determined by the Agilent 2100 Bioanalyzer (Agilent Technologies, USA). The Amino Allyl MessageAmp aRNA Kit is configured to incorporate the modified nucleotide, 5-(3-aminoallyl)-UTP (aaUTP) into the aRNA during in vitro transcription. Once purified and fragmented, the dye labeled aRNA was used for microarray hybridization. Labeled amplified RNA was hybridized to the 22K Mouse Oligo microarrays (Agilent Technologies)) according to the manufacturer's instructions. After hybridization microarrays were washed and scanned using GenePix 4000A (Axon Instruments,Inc.).