Ribosomal protein l (rpl) genes are broadly expressed in wild-type zebrafish endoderm. (A) Expression of rpl36a during zebrafish development. At 24 hpf, expression is broad in all tissues. During the course of development, expression becomes increasingly restricted to the larval endoderm. rpL9, 23, and 36 represent single color in situs; the remaining panels depict two-color in situ hybridization for the indicated rpL gene in blue and insulin in red. (B) rpl36a is strongly expressed in epithelial cells of the adult liver, intestine, and pancreas. (C) At 48 hpf, many rpL genes are expressed in a similar pattern in endodermal progenitors. L, liver; I, intestine; P, pancreas; Ex, exocrine pancreas; Isl, islet of Langerhans; PP, pancreatic progenitors; Sp, spleen. Color images available online at www.liebertpub.com/zeb

Mutations in the rpl23a gene result in compromised expansion of ptf1a-expressing pancreatic progenitor cells. (A) Expression of rpl23a during zebrafish development is broad at 24 hpf and becomes increasingly restricted to the larval endoderm during the course of development. (B) Strong expression of rpL23a is observed in adult liver, intestine, and pancreas. (C) An incross of rpl23a^{hi2582/ +} ;ptf1a:eGFP^jh1;ins:mCherry ^jh2 adult fish results in 72 hpf embryos exhibiting reduced brain and eye size (red arrowhead), edema, and poor yolk absorption (blue arrowhead). (D) Fraction of embryos from rpl23a^{hi2582/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 incross displaying gross developmental defects as assessed at 72 hpf (29% mutant, red; 71%, wild type, blue) compared with control embryos generated by rpl23a^{hi2582/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 outcross (2.8% mutant, red; 97.2% wild type, blue). (E) ptf1a-expressing pancreatic progenitor cells fail to expand normally in embryos generated by rpl23a^{hi2582/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 incross. (F) Activation of trypsin expression occurs normally in rpl23a^{hi2582/hi2582} hypoplastic pancreas. Images in (E) and (F) obtained at 72 hpf. (G) PCR genotyping of embryos individually imaged at 72 hpf confirms reduced pancreatic mass in both heterozygous rpl23ahi2582/ + ;ptf1a:eGFPjh1; ins:mCherryjh2 and homozygous rpk23a^{hi2582/hi2582};ptf1a:eGFP^jh1; ins:mCherry^jh2 embryos. ^(H) Incidence of abnormal pancreas development in embryos produced by either incross or outcross rpl23a^{hi2582/ +} ;ptf1a:eGFPjh1; ins:mCherry^jh2 adults, expressed as the fraction of phenotypic (red) and wild-type (blue) embryos evaluated at 72 hpf. (I) Decreased incidence of persistent hypoplastic pancreas at 96 hpf indicates recovery of normal pancreatic mass in rpl23ahi2582/ + heterozygotes. Color images available online at www.liebertpub.com/zeb

Mutations in the rpl6 gene result in compromised expansion of ptf1a-expressing pancreatic progenitor cells. (A) rpl6 expression is initially broad at 24 hpf, but high-level expression becomes increasingly restricted to the larval endoderm during the course of development. (B) Strong expression of rpl6 is observed in adult liver and pancreas. (C) An incross of rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 adult fish results in 72 hpf embryos exhibiting reduced brain and eye size (green arrowhead), edema (red arrowhead), and poor yolk absorption (yellow arrowhead). Asterisks indicate grossly phenotypic rpl6hi3655b/hi3655b embryos. (D) Fraction of embryos from rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 incross displaying gross developmental defects as assessed at 72 hpf (21% mutant, red; 79% wild type, blue) compared with control embryos generated by rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 outcross (1.7% mutant, red; 98.3% wild type, blue). (E) The adult pancreas is grossly and histologically normal in rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 heterozygotes. Note normal gross appearance of 7- month-old heterozygote, grossly normal pancreas including acinar cell mass (green), principal islet (yellow arrowhead), and secondary islets (white arrowheads), as well as normal adult histology. (F) ptf1a-expressing pancreatic progenitor cells fail to expand normally in embryos generated by rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 incross. (G) Activation of trypsin expression occurs normally in rpl6hi3655b/hi3655b hypoplastic pancreas. (H) Incidence of abnormal pancreas development in embryos produced by either incross or outcross rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1; ins:mCherry^jh2 adults, expressed as the fraction of phenotypic (red) and wild-type (blue) embryos evaluated at 72 hpf. (I) Decreased incidence of persistent hypoplastic pancreas at 96 hpf indicates recovery of normal pancreatic mass in rpl6hi3655b/ + heterozygotes. A, adipose tissue. Color images available online at www.liebertpub.com/zeb

Morpholino-mediated knockdown of p53 does fail to rescue defective expansion of ptf1a-expressing pancreas progenitor cells in rpl mutant embryos. (A) Injection of embryos produced by rpl23a^{hi2582/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 incross with 1 ng p53ATG MO does not rescue hypoplastic pancreatic phenotype. (B) Incidence of abnormal pancreas development among embryos produced by rpl23a^{hi2582/ +} ;ptf1a:eGFP^jh1;ins:mCherry ^jh2 incross injected with either p53ATG MO or mock control (phenotypic, red; wild type, blue). (C) Injection of embryos produced by rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1;ins:mCherry^jh2 incross with 1 ng p53ATG MO does not rescue hypoplastic pancreatic phenotype. (D) Incidence of abnormal pancreas development among embryos produced by rpl6^{hi3655b/ +} ;ptf1a:eGFP^jh1;ins:mCherry ^jh2 incross injected with either p53ATG MO or mock control (phenotypic, red; wild type, blue). Color images available online at www.liebertpub.com/zeb