TUBB4B and Diamond-Blackfan anemia: Several other proteins were decreased in three of the four DBA patients including phosphoribosyl pyrophosphate synthase-associated protein 2 (PRPSAP2), class IVb beta tubulin (TUBB2C), tubulin alpha-ubiquitous chain (TUBA1B), and intercellular adhesion molecule 4 (ICAM4).