CD34 and hydrops fetalis: We found that Nbn deficiency in HF progenitors promoted increased DNA damage signaling, stimulating Cdkn2a (p16INK4A) up-regulation, Trp53 stabilization, secretion of cytokines such as Il6 and Il1b, growth arrest leading to progressive reduction of Krt15-positive (Krt15+) and Cd34-positive (Cd34+) cells and premature hair loss.