ATM and ataxia telangiectasia: Mouse models deficient in ATM recapitulate accurate ataxia telangiectasia disease phenotypes,30, –, 32 but loss of ATM kinase activity causes early embryonic lethality in mice, indicating that inhibition of ATM kinase activity does not equate to loss of the ATM protein.33 It was speculated that embryonic lethality in mice with ATM kinase inactivity was the result of ATM kinase recruitment at DNA breaks, which may impair the function of other proteins by blocking their access to DNA damage.33