November 2015 Pathomechanistic model mice of sporadic ALS: Conditional ADAR2 knockout mice AR2

Pathomechanistic model mice of sporadic ALS:
Conditional ADAR2 knockout mice AR2

B6.Cg-Adarb1<tm1.1Skwa> Tg(SLC18A3-cre)KMisa (RBRC09428)

Courtesy of Shin Kwak, M.D., Ph.D.

(a) An AR2 mouse at 12 months of age (left panel) exhibits abnormal posture of the hind-limbs and the tail, as compared with normal posture of a control littermate (right panel). (b) Temporal profile of Cre expression in the motor neurons is indicated as the proportion of Cre-expressing and ADAR2-lacking motor neurons in the spinal anterior horns of the AR2 mice. Cre expression reached the maximum level (~50% of motor neurons) by postnatal week 5. AHCs: anterior horn cells. (c) The ADAR2^flox gene, transcripts of the Cre gene and the ADAR2^flox alleles before and after Cre-recombination in the laser-captured motor neurons were analyzed for each group by PCR. In addition, proportion of Q/R site-edited GluA2 in all the GluA2 expressed in motor neurons were calculated in ADAR2(−), ADAR2(+) motor neurons of AR2 mice and motor neurons of the littermate control mice (ADAR2^flox/flox mice and VAChT-Cre.Fast mice). ADAR2 (−) motor neurons expressed only unedited GluR2 (GluA2) mRNA, harboring the truncated ADAR2^floxgene and Cre transcripts, whereas ADAR2 (+) motor neurons expressed only edited GluR2 mRNA, carrying the full-length ADAR2^flox gene and did not express Cre. Motor neurons of the littermate control mice expressed full-length ADAR2 and only edited GluA2 mRNA.

Amyotrophic lateral sclerosis (ALS) is a progressive adult-onset motor neuron disease. Patients with ALS develop progressive muscle weakness resulting from both upper and lower motor neurons and ultimately lose the ability to breathe without mechanical support within a few years of onset. Although little is known about pathogenesis of sporadic ALS, which accounts for more than 90% of ALS cases, recent studies demonstrated that failure of adenosine-inosine (A-I) conversion at the glutamine/arginine (Q/R) site of GluA2, a subunit of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors, resulting from downregulation of an RNA-editing enzyme adenosine deaminase acting on RNA 2 (ADAR2) plays pivotal role in the ALS pathogenesis [1, 2]. AR2 mice mimic this molecular abnormality and exhibit ALS phenotype via mechanism mediated by Ca²⁺-permeable AMPA receptors that have Q/R site-unedited GluA2 in their subunit assembly [3]. In addition, TDP-43 pathology, a hallmark of ALS, is observed in the motor neurons devoid of ADAR2 immunoreactivity in the patients with ALS and ADAR2-lacking motor neurons of AR2 mice, in a calcium-dependent protease calpain-dependent manner [4, 5]. As restoration of ADAR2 activity by gene therapy using adeno-associated virus (AAV) rescues ALS phenotype and TDP-43 pathology in AR2 mice [6], the AR2 mice will be useful in ALS research aiming at both elucidating etiology and developing therapy.

Depositor	:	Keiji Itaka, M.D., Ph.D. & Shin Kwak, M.D., Ph.D. Laboratory of Clinical Biotechnology, Center for Disease Biology and Integrative Medicine Graduate School of Medicine, The University of Tokyo
Strain name	:	B6.Cg-Adarb1<tm1.1Skwa> Tg(SLC18A3-cre)KMisa
RBRC No.	:	RBRC09428
References	:	[1]	Kawahara Y, Ito K, Sun H, Aizawa H, Kanazawa I, Kwak S. Glutamate receptors: RNA editing and death of motor neurons. Nature; 427(6977):801, 2004.
		[2]	Hideyama T, Yamashita T, Aizawa H, Tsuji S, Kakita A, Takahashi H, Kwak S. Profound downregulation of the RNA editing enzyme ADAR2 in ALS spinal motor neurons. Neurobiol Dis.; 45(3):1121-8, 2012.
		[3]	Hideyama T, Yamashita T, Suzuki T, Tsuji S, Higuchi M, Seeburg PH, Takahashi R, Misawa H, Kwak S. Induced loss of ADAR2 engenders slow death of motor neurons from Q/R site-unedited GluR2. J Neurosci.; 30(36):11917-25, 2010.
		[4]	Aizawa H, Sawada J, Hideyama T, Yamashita T, Katayama T, Hasebe N, KimuraT, Yahara O, Kwak S. TDP-43 pathology in sporadic ALS occurs in motor neurons lacking the RNA editing enzyme ADAR2. Acta Neuropathol.; 120(1):75-84, 2010.
		[5]	Yamashita T, Hideyama T, Hachiga K, Teramoto S, Takano J, Iwata N, Saido T, Kwak S. A role for calpain-dependent cleavage of TDP-43 in amyotrophic lateral sclerosis pathology. Nat Commun.; 3:1307, 2012.
		[6]	Yamashita T, Chai HL, Teramoto S, Tsuji S, Shimazaki K, Muramatsu S, Kwak S. Rescue of amyotrophic lateral sclerosis phenotype in a mouse model by intravenous AAV9-ADAR2 delivery to motor neurons. EMBO Mol Med.; 5(11):1710-9, 2013.

November 2015
Contact: Shinya Ayabe, Ph.D.
Experimental Animal Division, RIKEN BioResource Center
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