Inactivation of the hereditary spastic paraplegia-associated Hspd1 gene encoding the Hsp60 chaperone results in early embryonic lethality in mice
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The mitochondrial Hsp60 chaperonin plays an important role in sustaining cellular viability. Its dysfunction is related to inherited forms of the human diseases spastic paraplegia and hypomyelinating leukodystrophy. However, it is unknown whether the requirement for Hsp60 is neuron specific or whether a complete loss of the protein will impair mammalian development and postnatal survival. In this study, we describe the generation and characterization of a mutant mouse line bearing an inactivating gene-trap insertion in the Hspd1 gene encoding Hsp60. We found that heterozygous mice were born at the expected ratio compared to wild-type mice and displayed no obvious phenotype deficits. Using quantitative reverse transcription PCR, we found significantly decreased levels of the Hspd1 transcript in all of the tissues examined, demonstrating that the inactivation of the Hspd1 gene is efficient. By Western blot analysis, we found that the amount of Hsp60 protein, compared to either cytosolic tubulin or mitochondrial voltage-dependent anion-selective channel protein 1/porin, was decreased as well. The expression of the nearby Hspe1 gene, which encodes the Hsp10 co-chaperonin, was concomitantly down regulated in the liver, and the protein levels in all tissues except the brain were reduced. Homozygous Hspd1 mutant embryos, however, died shortly after implantation (day 6.5 to 7.5 of gestation, Theiler stages 9–10). Our results demonstrate that Hspd1 is an essential gene for early embryonic development in mice, while reducing the amount of Hsp60 by inactivation of one allele of the gene is compatible with survival to term as well as postnatal life.
KeywordsChaperonin 60 Chaperonin 10 Embryonic development Gene knockout techniques Insertional mutagenesis, OmniBank®
The authors thank Birgitte Grann for her excellent technical assistance and Helle Christiansen for checking mice vaginal plugs each morning during the analysis of timed pregnancies. The work was supported by grants from the Ludvig and Sara Elsass Foundation, the Lundbeck Foundation, the EU 6th Framework Program, the Novo Nordisk Foundation, the Augustinus Foundation, “Elvira og Rasmus Riisforts Almenvelgørende Fond” [the Elvira and Rasmus Riisfort’s Common Charitable Foundation], and “Grosserer A.V. Lykfeldt og Hustrus Legat” [the Merchant A.V. Lykfeldt and Wife’s Grant], and Aarhus University.
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