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Genes Cells 2021 Jan 01;261:31-39. doi: 10.1111/gtc.12818.
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Periodic albinism of a widely used albino mutant of Xenopus laevis caused by deletion of two exons in the Hermansky-Pudlak syndrome type 4 gene.

The periodic albino mutant of Xenopus laevis is a recessive mutant, in which reduced amounts of melanin appear in the retinal pigment epithelium (RPE) and in melanophores at the late embryonic stage, after which both RPE and melanophores gradually depigment. Three types of pigment cells (melanophores, iridophores and xanthophores) have been reported to be affected in this albino. However, the causative gene of the periodic albinism remains unknown. Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder that affects humans and mice, which is caused by defective biogenesis of lysosome-related organelles (LROs). Two subgenomes (L and S) are present in the allotetraploid frog X. laevis. Comparison of genes between the chromosomes 1L and 1S revealed that the HPS type 4 (hps4) gene was present only in chromosome 1L. In the albino mutant, a 1.9 kb genomic deletion in the hps4.L gene including exons 7 and 8 caused a premature stop codon to create a truncated Hps4 protein. Injection of wild-type hps4.L mRNA into mutant embryos rescued the albino phenotype. These findings indicate that hps4 is a causative gene for the periodic albinism in X. laevis. The phenotype of this mutant should be reassessed from the perspective of LRO biogenesis.

PubMed ID: 33147376
PMC ID: PMC7839477
Article link: Genes Cells

Species referenced: Xenopus laevis
Genes referenced: asphd2 crybb1 hps1 hps4 hps5 sez6l srrd tpst2

Disease Ontology terms: Hermansky-Pudlak syndrome 4
Phenotypes: Xla.hps4{m} (Fig. 1 bfdh)

Article Images: [+] show captions
References [+] :
Anderson, Hermansky-Pudlak syndrome type 4 (HPS-4): clinical and molecular characteristics. 2003, Pubmed