lnduced Pluripotent Stem CelIs to Study Neutrophil Development in Barth Syndrome

Taco Kuijpers, MD, PhD, Amsterdam University Medical Center

Barth Syndrome (BTHS) is known as a rare inherited disease characterized by a dilated cardiomyopathy, proximal skeletal myopathy, growth retardation and neutropenia. The disease is caused by pathogenic variants in the X-linked TAZ gene in males, encoding TAFAZZIN, a translocase. BTHS is a mitochondrial disorder of cardiolipin metabolism and organic aciduria with an excess of 3-methylglutaconic acid (1 ). Being notorious as one of several congenital neutropenia syndromes, we have studied neutrophil behavior in the past and observed a remarkable phenotype of circulating neutrophils with enhanced binding of the phospatidylserine (PS) lipid-binding annexin-V. Binding of fluorescently labeled annexin-V to cells including neutrophils is considered a typical hallmark of a process of programmed cell death or apoptosis. Since we could not detect any other sign of premature apoptosis of the circulating neutrophils by additional parameters or assays, we believed at that time that the annexin-V binding could be the result of a disturbed lipid composition of the plasma membrane and oxidative stress (2).

To study the underlying process of aberrant neutrophil development in BTHS we would need multiple bone marrow samples for further clarification of the biochemical findings in the remaining neutrophils in BTHS patients. Considering the invasive nature of these procedures, we have renounced from such further studies. Having developed a methodology for generating mature and fully functional human neutrophils from induced pluripotent cell lines (iPSCs), we have now the opportunity and propose again to investigate the pathophysiotogy of neutropenia and neutrophil development in BTHS in detail without the need for multiple requests of patient materials by current technology and unbiased omics approaches.