C57BL/6J-Serpina1^em3Chmu/J

Stock number: 035015
Product name: AAT KO line 31C

Research areas: Internal/Organ Research

Description

This strain ships with remnant UID MiniMax microchips implanted subcutaneously in the back. For more information on these RFID chips, including our FAQ, please visit our Mouse Identification page.

AAT (line 31C) knockout mice carry a 74 kb deletion in exon 2 of the Serpina1 cluster resulting in the absence of expression of 5 Serpina1 genes (a, b, c, d, and e). LPS airway challenge to AAT (α1 antitrypsin) KO mice results in characteristics of emphysematous lung. Mice develop spontaneous emphysema by 50 weeks of age. This strain may be useful for studying COPD and emphysema.

Detailed description

Serpina1 (serine (or cysteine) peptidase inhibitor, clade A, member 1 cluster) encodes a protease inhibitor targeting neutrophil elastase. In humans, the leading cause of chronic obstructive pulmonary disease (COPD) is an α1 antitrypsin (SERPINA1 or AAT) deficiency. In mice there are 6 Serpina1 paralogs of which 5 are expressed in the liver where AAT is produced and secreted into the circulation. Once in the lungs AAT protects the alveoli and interstitial elastin by inactivating neutrophil elastase. The Serpina1 cluster expressed in the liver contains, in order, Serpina1b, 1d, 1a, 1c, and 1e spanning 230 kb on chromosome 12. The AAT (line 31C) knockout mice were created through CRISPR/Cas9 genome editing to excise Serpina1a and Serpina1c, with a 74 kb deletion in exon 2 of the Serpina1 cluster, resulting in the absence of expression of 5 Serpina1 genes (a, b, c, d, and e). Homozygous AAT null mice have undetectable levels of circulating AAT and are viable and fertile, however,  progeny from homozygote x homozygote matings die prior to weaning. Following mild LPS airway challenge AAT KO mice develop characteristics of emphysematous lung including a shift (up and left) in pressure volume (PV) loop, increased inspiratory capacity, and increased lung volume and surface area. Mice develop the early signs of spontaneous emphysema by 35 weeks of age and by 50 weeks present a clear emphysema phenotype.

Development

CRISPR/cas9 endonuclease-mediated genome editing was used to target conserved exon 2 of the Serpina1 (serine (or cysteine) peptidase inhibitor, clade A, member 1 cluster) cluster. Four guide RNAs and Cas9 endonuclease were introduced into C57BL/6J-derived fertilized eggs by intracytoplasmic microinjection. Embryos were transferred to pseudopregnant females, and correctly targeted pups were bred to C57BL/6J mice for germline transmission. Line 31C carries a 74 kb deletion beginning at 103822963 (ending at 103897826), which includes Serpina1a and Serpina1c. Serpina1b, 1d and 1e genes all carry a deletion in exon 2. Mice were maintained on the C57BL/6J background. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes.

Allele

Symbol: Serpina1^em3Chmu
Name: endonuclease-mediated mutation 3, Christian Mueller
MGI accession ID: MGI:6358590
Generation method: Endonuclease-mediated
Attributes: Null/Knockout
Synonyms: 31C
Marker symbol: Serpina1
Marker name: serine (or cysteine) peptidase inhibitor, clade A, member 1 cluster
Marker synonyms: [a]1-antitrypsin; [a]1-PI; [a]1-proteinase inhibitor; Aat; alpha-1 antiproteinase; antitrypsin; Pre; Pre-1; Spi1; Spi-1
Chromosome: 12
Strain of origin: C57BL/6J
Molecular note: CRISPR/Cas9 technology is used to disrupt five highly homologous gene paralogs through the targeting of exon 2 using a combination of four gRNAs, deleting 74 kb (103822963-103897826), resulting in the excision of Serpina1a and 1c. Null status was confirmed by transcriptome analysis. Western blot confirmed absence of the alpha1-antitrypsin protein in serum.