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The intraflagellar transport protein ift80 is essential for photoreceptor survival in a zebrafish model of jeune asphyxiating thoracic dystrophy.

ABSTRACT: PURPOSE. Jeune's asphyxiating thoracic dystrophy (JATD) is an autosomal recessive disorder with symptoms of retinal degeneration, kidney cysts, and chondrodysplasia and results from mutations in the ift80 gene. This study was conducted to characterize zebrafish lacking ift80 function for photoreceptor degeneration and defects in ciliogenesis to establish zebrafish as a vertebrate model for visual dysfunction in JATD and to determine whether ift80 interacts genetically with Bardet-Biedl syndrome (BBS) genes. METHODS. Zebrafish were injected with morpholinos (MOs) targeted to the ift80 gene. Retinas were analyzed by histology, transmission electron microscopy, and immunohistochemistry. Ear and kidney cilia were analyzed by whole-mount immunostaining. Intraflagellar transport (IFT) particle composition was subjected to Western blot analysis. Genetic interactions were tested by coinjection of MOs against ift80 and bbs4 or bbs8 followed by in situ hybridization. RESULTS. Zebrafish lacking ift80 function exhibited defects in photoreceptor outer segment formation and photoreceptor death. Staining with opsin antibodies revealed opsin mislocalization in both rods and cones. Ultrastructural analysis showed abnormal disc stacking and shortened photoreceptor outer segments. The kinocilia of the ear and motile cilia in the kidney were shorter and reduced in number. Western blot analysis revealed a slight increase in the stability of other IFT proteins. Coinjection of MOs against ift80 and BBS genes led to convergent-extension defects. CONCLUSIONS. Zebrafish lacking ift80 exhibited defects characteristic of JATD. Because the developing outer segments degenerated, Ift80 could possibly act as a maintenance factor for the IFT particle.

SUBMITTER: Hudak LM

PROVIDER: S-EPMC2893332 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Jeune syndrome, or asphyxiating thoracic dystrophy (JATD), is a rare autosomal recessive skeletal dysplasia with heterogeneous genetic and clinical phenotypes, which primarily affects cartilage and bone development. Herein, we report a patient with a lethal form of SRTD3 without polydactyly (JATD), which led to severe restrictive lung disease and fatal respiratory failure. A full-term boy was born to a 30-year-old mother who was known to have hypothyroidism and was on thyroxine. The parents were first-degree cousins and had one healthy older son. Fetal ultrasound showed a cephalic fetus, normal amniotic fluid and a fundal placenta. All long bones and ribs were below the 1% percentile. The femur was bowed with no fractures or signs of significant demineralization at time of imaging. Head and abdominal circumference were within normal range. An echocardiogram on the 2nd day of life showed severe pulmonary hypertension (PHTN). Nitric oxide was started due to the presence of persistent hypoxia and severe PHTN. The patient continued to require high cardiorespiratory support, but the medical condition worsened, and respiratory failure persisted. The patient died of severe respiratory failure at 16 days of life due to respiratory insufficiency secondary to a severely restricted thoracic cage. Whole-exome sequencing (WES) revealed a homozygous mutation in the DYNC2H1 (NM_001377.3) gene, namely, the c.9041G>T NP_001368.2: p.(Arg3014Ile) missense variant, which results in the substitution of the arginine codon at amino acid position 3014 with an isoleucine codon. The phenotyping of the patient's JATD and the detection of a homozygous variant in the DYNC2H1 gene confirmed the diagnosis of short-rib thoracic dysplasia-3 without polydactyly. In summary, the patient had isolated skeletal anomalies without polydactyly or other organ involvement. Additionally, the infant had severe PHTN on top of the respiratory failure, which eventually caused death. Considerably more work will need to be done to determine the clinical spectrum of JATD and understand its genetic heterogeneity.

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The intraflagellar transport protein ift80 is essential for photoreceptor survival in a zebrafish model of jeune asphyxiating thoracic dystrophy.

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