A missense mutation in Atf2 in standard poodles with fatal neonatal encephalopathy

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Neonatal encephalopathy with seizures (NEWS) is a previously undescribed autosomal recessive disease in Standard Poodles. Affected puppies are small and weak at birth. Many died in their first week of life and surviving puppies developed ataxia, a wholebody tremor and, by 4-to-6 weeks of age, severe generalized clonic-tonic seizures. None have survived past six weeks of age. Cerebella from affected puppies were reduced in size and often contained dysplastic foci consisting of clusters of intermixed granule and Purkinje neurons. A panel of 304 microsatellite markers was used to genotype DNA from a 78-member Standard Poodle family containing 20 affected puppies. Linkage analysis localized the disease locus to an 8.7 Mb segment of CFA36 between markers REN179H15 and REN252E18 with LOD scores exceeding 7.0. Fine mapping with 11 additional markers restricted the target region to a 2.87 Mb chromosomal segment containing 26 genes including LOC478806, the canine ortholog of human ATF2. This gene encodes activating transcription factor 2 (ATF-2) which participates in the cellular responses to a wide variety of physiologic and pathologic stimuli and is required for the normal development and function of the central nervous system. All coding regions of the ATF2 gene from a NEWS-affected puppy were amplified and sequenced revealing a T->G transversion that predicts a methionine-to-arginine missense mutation at amino acid position 51. Methionine-51 is part of a hydrophobic docking site for the mitogenactivated protein kinases that activate ATF-2. Thus, substitution of an arginine at position 51 is expected to interfere with ATF-2 activation. The mutant allele co-segregated with the disease in the Standard Poodle family: all 20 NEWS-affected puppies in this family were homozygous for the mutant G allele. The 58 clinically normal family members were either G/T heterozygotes or homozygous for the ancestral T allele. One hundred eighteen phenotypically normal representatives of other breeds were all homozygous for the ancestral T allele. There are no previous reports of spontaneous ATF2 in people or animals; however, atf2-knockout mice have cerebellar lesions that are similar to those in the puppies with NEWS. A pyrosequencing-based DNA test is being used as the basis of a program to eradicate this neonatal encephalopathy in Standard Poodles by selective breeding.