# Pyruvate kinase deficiency modifies sickle hemoglobin carrier and sickle cell disease phenotypes in mice

## TL;DR

This study shows that pyruvate kinase deficiency affects sickle cell disease and carrier phenotypes in mice, causing anemia and reducing sickling.

## Contribution

The study reveals how Pklr mutations modify sickle cell disease and carrier phenotypes in mice through novel CRISPR-generated models.

## Key findings

- PKR-deficient mice showed severe anemia and iron deposits in spleen and liver.
- PKR deficiency decreased sickling in AS and SS mice despite causing extramedullary hematopoiesis.
- Pklr mutations differentially impact sickle cell trait and disease in mouse models.

## Abstract

Growing evidence indicates that PKLR, the gene for pyruvate kinase (PK), is a genetic modifier of the sickle cell phenotype. Coinheritance of specific PKLR variants is associated with increased pain-related hospitalization and can trigger sickle cell disease (SCD) phenotypes in asymptomatic carriers. PK deficiency disrupts RBC glycolysis, leading to ATP deficits and accumulation of 2,3-diphosphoglycerate, which exacerbates sickling in SCD. Using CRISPR-Cas9, we generated null mutations in Pklr [Pklr(13ntdel/13ntdel) or Pklr(246ntdel/246ntdel)] specific for the RBC isoform (PKR) in Townes mice that were homozygous (SS) or heterozygous (AS) for the human sickle globin gene, or homozygous for human hemoglobin A (AA, controls), to investigate the effect of PKR deficiency on the sickle phenotype in mice. PKR-deficient AA and AS mice developed severe anemia, reticulocytosis, and substantial spleen and liver iron deposits. Unlike what is observed in humans, PKR deficiency in AS and SS mice surprisingly decreased sickling, but it was also associated with increased extramedullary hematopoiesis and mitochondrial retention in mature RBCs. These results demonstrate the differential effect of Pklr mutations on the phenotype of both AS and SS mouse models, offering insights into the complex role of PKR deficiency in SCD pathology.

Pklr mutations associated with pyruvate kinase deficiency modify the phenotype of sickle cell trait and sickle cell disease in mouse models