Expression and localization of proteins in tissue determines anatomy and physiology, and thus provides a clue to pathology. However, it is strenuous to identify the expression and localization of multiple targets using conventional immunostaining technique, especially when there is no specific antibody, nor explicit assumption, for target proteins. Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry is a proteomic technique to simultaneously map multiple targets in a frozen tissue section. Using this technique, we analyzed protein expression in heart, and in testis as a reference sample, in 129/sv mice. Spatial distribution of at least 57 individual proteins was simultaneously identified at 100 um resolution. Among them, cardiac alpha actin, cardiac troponin T, tropomyosin alpha-1 chain, titin, myosin light chain 1 (MYL1), myosin light chain 3 (MYL3), myosin-6 were exclusively expressed in the heart. MYL1 and MYL3, the altered expression of which is associated with heart failure, were localized in the atrium and in the ventricle, respectively, as expected. Interestingly, protein expression profile of cysteine-rich protein 2 and myomesin-1 is exactly as predicted from mRNA expression, namely more in the heart and less in the testis. Expression level of housekeeping genes, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and beta actin, was similar between the heart and the testis. These results suggest that MALDI imaging may provide a new platform for analysis of pathology and subsequent application to diagnosis of heart diseases.

1. Simultaneous mapping of multiple proteins
in heart using matrix-assisted laser
desorption/ionization imaging mass
spectrometry
Ken Takahashi
Department of Cardiovascular Physiology
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences
Okayama University, Japan

2. Background
• Expression and localization of proteins in
tissue determines anatomy and physiology,
and thus provides a clue to pathology.
• However, it is strenuous to identify the
expression and localization of multiple targets
using conventional immunostaining technique.

3. MALDI-IMS
Int J Oncol, 2015. 46(3): p. 893-906

4. ResultsHeart(n=2)
4 mm
Testis(n=2)

5. Results
No. Accession Protein
MW
[kDa]
1 MYH6 Myosin-6 OS=Mus musculus 223.4
2 TNNT2 Troponin T, cardiac muscle 35.8
3 ACTC Actin, alpha cardiac muscle 1 42.0
4 MYL3 Myosin light chain 3 22.4
5 MYH8 Myosin-8 OS=Mus musculus 222.6
6 ACON Aconitate hydratase, mitochondrial 85.4
7 MYPC3 Myosin-binding protein C, cardiac-type 140.5
8 HBA Hemoglobin subunit alpha 15.1
9 G3P Glyceraldehyde-3-phosphate dehydrogenase 35.8
10 TPM1 Tropomyosin alpha-1 chain 32.7
11 TITIN Titin 3904.1
12 ACTG Actin, cytoplasmic 2 41.8
13 HBB1 Hemoglobin subunit beta-1 15.8
14 KCRS Creatine kinase, sarcomeric mitochondrial 47.4
15 ETFA Electron transfer flavoprotein subunit alpha, mitochondrial 35.0
16 HBB2 Hemoglobin subunit beta-2 15.9
17 ATPA ATP synthase subunit alpha, mitochondrial 59.7
18 MDHM Malate dehydrogenase, mitochondrial 35.6
19 TNNI3 Troponin I, cardiac muscle 24.2
20 KCRM Creatine kinase M-type 43.0
21 ALDOA Fructose-bisphosphate aldolase A 39.3
22 CRIP2 Cysteine-rich protein 2 22.7
23 MYG Myoglobin 17.1
24 THIM 3-ketoacyl-CoA thiolase, mitochondrial 41.8
25 IDHP Isocitrate dehydrogenase [NADP], mitochondrial 50.9
26 ATPB ATP synthase subunit beta, mitochondrial 56.3
27 COQ9 Ubiquinone biosynthesis protein COQ9, mitochondrial 35.1
28 MLRV Myosin regulatory light chain 2, ventricular/cardiac muscle isoform 18.9
29 ATP5J ATP synthase-coupling factor 6, mitochondrial 12.5
30 CSRP3 Cysteine and glycine-rich protein 3 20.9
31 UCRI Cytochrome b-c1 complex subunit Rieske, mitochondrial 29.3
32 MYH3 Myosin-3 223.7
No. Accession Protein
MW
[kDa]
33 COX5A Cytochrome c oxidase subunit 5A, mitochondrial 16.1
34 YBOX1 Nuclease-sensitive element-binding protein 1 35.7
35 QCR7 Cytochrome b-c1 complex subunit 7 13.5
36 MDHC Malate dehydrogenase, cytoplasmic 36.5
37 ACTBL Beta-actin-like protein 2 42.0
38 QCR2 Cytochrome b-c1 complex subunit 2, mitochondrial precursor 48.2
39 ETFB Electron transfer flavoprotein subunit beta 27.6
40 LDHB L-lactate dehydrogenase B chain 36.5
41 DESM Desmin OS=Mus musculus 53.5
42 HSP7C Heat shock cognate 71 kDa protein 70.8
43 ECI1 Enoyl-CoA delta isomerase 1, mitochondrial 32.2
44 AT2A2 Sarcoplasmic/endoplasmic reticulum calcium ATPase 2 114.8
45 ECHA Trifunctional enzyme subunit alpha, mitochondrial 82.6
46 THIL Acetyl-CoA acetyltransferase, mitochondrial 44.8
47 VINC Vinculin 116.6
48 CISY Citrate synthase, mitochondrial 51.7
49 EF1A2 Elongation factor 1-alpha 2 50.4
50 MYL1 Myosin light chain 1/3, skeletal muscle isoform 20.6
51 ACADM Medium-chain specific acyl-CoA dehydrogenase, mitochondrial 46.5
52 ACTN2 Alpha-actinin-2 103.8
53 NDUS6 NADH dehydrogenase [ubiquinone] iron-sulfur protein 6, mitochondrial 13.0
54 CYC Cytochrome c, somatic 11.6
55 SCOT1 Succinyl-CoA:3-ketoacid coenzyme A transferase 1, mitochondrial 56.0
56 AT1A1 Sodium/potassium-transporting ATPase subunit alpha-1 112.9
57 ACTB Actin, cytoplasmic 1 41.7
58 YBOX1 Nuclease-sensitive element-binding protein 1 35.7
59 CALR Calreticulin 48.0
60 PRM2 Protamine-2 13.6
61 HSP72 Heat shock-related 70 kDa protein 2 69.6
62 RL18 60S ribosomal protein L18 21.6
63 SP17 Sperm surface protein Sp17 17.3
64 ALDOA Fructose-bisphosphate aldolase A 39.3

6. Conclusion
MALDI imaging may provide a new platform for
analysis of pathology and subsequent
application to diagnosis of heart diseases.

7. Acknowledgment
This work was supported by JSPS KAKENHI
Grant Number JP16K01356