Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to progressive familial heart block ?
    ### Response:
    Mutations in the SCN5A and TRPM4 genes cause most cases of progressive familial heart block types IA and IB, respectively. The proteins produced from these genes are channels that allow positively charged atoms (cations) into and out of cells. Both channels are abundant in heart (cardiac) cells and play key roles in these cells' ability to generate and transmit electrical signals.
    