Mouse brain expression patterns of Spg7, Afg3l1, and Afg3l2 transcripts, encoding for the mitochondrial m-AAA protease.
BACKGROUND
The m-AAA (ATPases Associated with a variety of cellular Activities) is an evolutionary conserved metalloprotease complex located in the internal mitochondrial membrane. In the mouse, it is a hetero-oligomer variably formed by the Spg7, Afg3l1, and Afg3l2 encoded proteins, or a homo-oligomer formed by either Afg3l1 or Afg3l2. In humans, AFG3L2 and SPG7 genes are conserved, whereas AFG3L1 became a pseudogene. Both AFG3L2 and SPG7 are involved in a neurodegenerative disease, namely the autosomal dominant spinocerebellar ataxia SCA28 and a recessive form of spastic paraplegia, respectively.


RESULTS
Using quantitative RT-PCR, we measured the expression levels of Spg7, Afg3l1, and Afg3l2 in the mouse brain. In all regions Afg3l2 is the most abundant transcript, followed by Spg7, and Afg3l1, with a ratio of approximately 5:3:1 in whole-brain mRNA. Using in-situ hybridization, we showed that Spg7, Afg3l1 and Afg3l2 have a similar cellular pattern of expression, with high levels in mitral cells, Purkinje cells, deep cerebellar nuclei cells, neocortical and hippocampal pyramidal neurons, and brainstem motor neurons. However, in some neuronal types, differences in the level of expression of these genes were present, suggesting distinct degrees of contribution of their proteins.


CONCLUSIONS
Neurons involved in SCA28 and hereditary spastic paraplegia display high levels of expression, but similar or even higher expression is also present in other types of neurons, not involved in these diseases, suggesting that the selective cell sensitivity should be attributed to other, still unknown, mechanisms.
Sacco
Tiziana
T
Section of Physiology of the Department of Neuroscience, University of Torino and National Institute of Neuroscience-Italy, Torino, Italy.
Boda
Enrica
E
Hoxha
Eriola
E
Pizzo
Riccardo
R
Cagnoli
Claudia
C
Brusco
Alfredo
A
Tempia
Filippo
F
D049069:ATP-Dependent Proteases; D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000235:genetics*; D000818:Animals; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D001931:Brain Mapping; D004734:Energy Metabolism / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D008666:Metalloendopeptidases / Q000235:genetics*; D051379:Mice; D051336:Mitochondrial Membranes / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000201:enzymology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015419:Spastic Paraplegia, Hereditary / Q000201:enzymology; D020754:Spinocerebellar Ataxias / Q000201:enzymology
D012333:RNA, Messenger; D049069:ATP-Dependent Proteases; C546907:Afg3l1 protein, mouse; C542395:Afg3l2 protein, mouse; D008666:Metalloendopeptidases; C491813:Spg7 protein, mouse; C114583:m-AAA proteases; D000251:Adenosine Triphosphatases; D000074183:ATPases Associated with Diverse Cellular Activities