EM analyses of ultrathin sections prepared from the lungs of the Monocrotaline (MCT)- rat model of PAH confirmed that ITSN deficiency and the presence of the EHITSN induces a similar lung phenotype as in the EHITSN-transduced K0ITSN+/- mouse (i.e., leaky IEJs and increased occurrence of pleomorphic morphological structures functioning as morphological intermediates of alternative endocytic pathways), Figure 5. Here, ITSN1 is linked to pulmonary arterial hypertension.