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Digitale Dissertation

Christina Maria Nock :
From Genome to Proteome: Genetic and physical mapping of mouse brain proteins
Vom Genom zum Proteom: Genetische und Physikalische Kartierung von Gehirnproteinen der Maus

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Abstract

Untitled Document SUMMARY

After completing genome sequencing of organism and after identification of the coding sequences virtually every protein of the organism can be assigned to its structural or coding gen, provided enough information exists about the primary structure of the protein (amino acid sequence, (e.g. tryptic) peptide masses). Unknown stays yet to which extend the appearance of a protein depends on its gen and to which extend it depends on further coding DNA-sequences. These are genes, that influence expression or modification of other proteins. In respect of these questions about regulation and modification we performed genetic mapping of polymorphic proteins in the mouse. The investigation of brain proteins of the two mouse species Mus musculus and Mus spretus with high resolution two-dimensional electrophoresis had revealed 1324 quantitative or qualitative protein polymorphisms out of a total number of 8700 cytosolic proteins (Klose 1999b). An European Collaborative Interspecific Backcross project (EUCIB) was founded for high resolution mapping of the mouse genome, based on 1000 backcross animals from the two species Mus musculus and Mus spretus. DNA-markers were spaced 0.61cM on average. The mapping of 1324 protein polymorphisms on the genetic map of the mouse was based on the analysis of the polymorphisms in 64 of the 1000 backcross animals of the EUCIB cross. Because a part of the 64 backcross animals were not sufficiently genotyped with DNA-markers, we started with using additional markers based on IRS-PCR to substantially increase the marker density as a prerequisite for mapping the protein polymorphisms. This aimed at fully revealing the existing recombinations in all of the 64 backcross animals and utilizing them for the mapping of polymorphic proteins. IRS-PCR markers were used because they can be used without knowing any genomic sequence information. They are generated using a single primer, e.g. the primer B1R for the repetitive SINE-element B1 of the mouse. IRS-PCR products of genomic DNA from Mus musculus revealing a quantitative polymorphism between Mus musculus and Mus spretus were used here for genotyping of up to 300 backcross animals from the EUCIB cross. The integration of 70 IRS-PCR markers and 9 microsatellite markers in the markerframework of 90 anchor markers provided by EUCIB established an improved, sound framework for positioning of the polymorphic proteins on the genetic map of the mouse. The software MAPMAKER/EXP 3.0 was used to build a genetic map out of DNA- and protein polymorphisms.
The results showed: 664 of the 1324 polymorphic protein spots could be mapped on the genetic map of the mouse. Spots showing identical inheritence and the same type of variation were given the same name and defined as a 'homogeneous spot family'. The 664 mapped spots represented therefore 409 variants. 360 variants could be placed on the mouse chromosomes. As threshold for the ordering of protein polymorphisms between DNA-markers a logarithmic odds ratio of 2.5 was applied. 49 of the 409 variants showed only linkage to a chromosome.
With the procedure used here for mapping polymorphisms based on mendelian inheritance we could only assess monogenetically caused polymorphisms. For the variants that showed linkage to a chromosome only as well as the 660 of the 1324 polymorphic spots that didn't show a mendelian segregation pattern at all, it can be concluded that the polymorphisms are caused by the effects of not only one but several genes. The polymorphisms of these spots are probably caused by additional loci

other than the protein coding gene locus itself. To find out which proteins are represented by the 664 mapped spots or 409 variants mass spectrometry was used to identify the spots. The aim was, to recognize spot families and to find all the isospots that represent the same protein. Until now about 200 protein spots could be identified. Next to spots belonging to homogeneous spot families mentioned above 25 heterogeneous spot families could be recognized. A heterogeneous spot family contains spots that are all identified as the same protein, but the single spots show different types of polymorphisms. The genetic analysis showed, that some of the polymorphic spots mapped to the known position of the coding gene whereas others mapped to an unexpected chromosomal location. These mapping positions reveal probably protein-modifying or regulating genes. The identified proteins belong to several different classes: 103 protein spots represented 70 proteins which were mapped newly in the mouse. 20 proteins had already been mapped and were confirmed in our approach. These polymorphisms were considered as based on coding gene polymorphisms, where the polymorphism reflects different alleles of the gene in the two mouse species. A third class contained 21 proteins that mapped differently from the known mapping position in mouse or the human orthologue. For example, spots of the heterogeneous spot family of 'Gamma Enolase' belong to all three classes: four mobility variants map to the known position of the 'Gamma Enolase' gen on chromosome 6, two variants map to different positions on chromosome 6, one on chromosome 15 and one spot is non-variant, probably due to loss of the coding-gene-based variation during degradation of the protein. Counting single spots that are identified by mass spectrometry 70% of the polymorphisms are based on the protein-coding gene whereas 30% can be lead back onto modifying or regulating gene locus.
In the examination presented the cytosolic fraction of mouse brain was investigated. Further investigation on the membrane fraction and on several additional mouse tissues (liver, heart, kidney and muscle) will follow. The analysis of liver and heart proteins revealed already that the majority of spots overlap with spots also present in the brain 2D-pattern. The genetic analysis of the polymorphisms will show to which extend regulating and modificating loci are responsible for organ specificity of proteins.


Table of Contents

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TITELBLATT,INHALTSVERZEICHNIS

I.	EINLEITUNG.................................................................................1

1.1	Das Konzept einer Large-Scale Analyse in der Biologie......................................1

1.2	Funktionelle Genomanalyse..................................................................3

1.3	Proteomanalyse - die Wiederentdeckung der Proteine.........................................4

1.4	Proteomanalyse - Stand der Technik.........................................................7
1.4.1    Gelsysteme.................................................................................7
1.4.2    Proteinextraktion..........................................................................9
1.4.3    Quantitative Analyse von 2D-Mustern.......................................................10
1.4.4    Bildanalyse von 2D-Mustern................................................................10
1.4.5    Massenspektrometrie von Proteinen.........................................................11

1.5	Proteomanalyse im Vergleich zur Genomanalyse..............................................12
1.5.1	Methodische Aspekte.......................................................................12
1.5.2    Syntheserate und zelluläre Konzentration der Proteine.....................................13
1.5.3    Posttranslationale Modifikationen der Proteine............................................13

1.6	Die genetische Analyse als Bindeglied zwischen Genom und Proteom..........................15
1.6.1	Proteinpolymorphismen.....................................................................15
1.6.2	Das Netzwerk zwischen Gen- und Proteinebene...............................................17

1.7	Genetische und physikalische Kartierung von Proteinen der Maus
   	Ansatzpunkte zur eigenen Untersuchung.....................................................18
1.7.1    Ein Europäisches Kollaborationsprojekt zur genetischen Kartierung der Maus(EUCIB).........18
1.7.2    Die physikalische Karte des Mausgenoms....................................................19
1.7.3    Ansatz und Ziele der eigenen Untersuchungen...............................................20


II.	MATERIAL UND METHODEN.....................................................................22

2.1	Molekulargenetische Untersuchungen........................................................22
2.1.1	Material..................................................................................22
	Enzyme....................................................................................22
	Grössenstandards..........................................................................22
	Oligonukleotide...........................................................................22
	Gefässe...................................................................................23
	DNA- und Protein-bindende Membranen.......................................................23
	Geräte....................................................................................23
	Puffer und Medien.........................................................................23
	Klonbanken................................................................................24
2.1.2	Versuchstiere.............................................................................25
2.1.3	Methoden..................................................................................28
	Mikrobiologische Methoden.................................................................28
	Molekularbiologische Methoden.............................................................28

2.2	Biochemische Untersuchungen...............................................................34
2.2.1	Material..................................................................................34
	Chemikalien...............................................................................34
	Geräte....................................................................................34
	Lösungen..................................................................................34
2.2.2	Versuchstiere.............................................................................35
2.2.3	Methoden..................................................................................35
	Präparation von Gehirnen..................................................................35
	Proteinextraktion.........................................................................35
	2D-Elektrophorese.........................................................................36
	Färbetechniken............................................................................36
	Massenspektrometrie.......................................................................37

2.3	Erfassung der genetischen Daten aus 2D-Proteinmustern.....................................38

2.4	Genkartierung.............................................................................40
2.4.1	Zusammenstellen der Protein- und DNA-Segregationsdaten in Dateien.........................40
2.4.2	Berechnung der genetischen Karte..........................................................40
	Untersuchung paarweiser Kopplung (two-point linkage)......................................41
	Mehrpunkt-Analyse (multipoint analysis)...................................................41
	Kontrollen................................................................................41


III.	ERGEBNISSE................................................................................42

3.1	Segregationsanalyse von DNA-Polymorphismen................................................42
3.1.1	Bedeutung und Häufigkeit von DNA-Polymorphismen und ihre Darstellung mittels
    	genetischer Marker: RFLP-Marker, SSLP-Marker und IRS-PCR-Marker...........................42
3.1.2	Vorgehensweise bei der Genotypisierung der B1-Mäuse durch IRS-PCR-Marker..................44
3.1.3	Kartierungsdaten der IRS-PCR-Marker.......................................................46
3.1.4	Datenqualität.............................................................................49
3.1.5	Einsatzmöglichkeiten der IRS-PCR Marker für andere Mäusekreuzungen........................51
3.1.6	Kartierungsdaten für Mikrosatellitenmarker................................................53

3.2	Segregationsanalyse von Protein-Polymorphismen - Ergebnisse aus 2D-Mustern................55

3.3	Eine genetische Karte aus DNA- und Proteinpolymorphismen..................................57
3.3.1	Vorbemerkung zur Genkartierung............................................................57
3.3.2	Genkartierungsdaten.......................................................................59
	Der Ausgangspunkt der Kartierung: die Rahmenkarte (framework map).........................59
	Erweiterung der Rahmenkarte mit IRS-PCR und Mikrosatellitenmarkern........................59
	Integration von Proteindaten in das DNA-Marker Netzwerk...................................64
	Integration der MSO-Marker des EUCIB Projektes in die genetische Karte....................65
3.3.3	Datenqualität.............................................................................66
3.3.4	Verteilung der kartierten Proteine auf die einzelnen Chromosomen
    	-  Vergleich mit der MBx-Datenbank........................................................66
	Die Kartenlänge in Abhängigkeit von der Kartierungsfunktion...............................69

3.4	Identifizierung von genetisch kartierten Proteinspots durch Massenspektrometrie...........71

3.5	Physikalische Kartierung nichtpolymorpher Proteinspots von 2DE-Gelen......................77
3.5.1	Vorgehensweise............................................................................77
3.5.2	Proteinidentifizierung und Identifizierung eines entsprechenden cDNA-Klons................78
3.5.3	Kartierung von I.M.A.G.E cDNA-Klonen mittels IRS-PCR auf YAC-Klonen.......................80
	Identifizierung von genomischen BAC-DNA-Klonen für IRS-PCR................................80
	Herstellung der IRS-PCR Produkte von genomischen BAC-DNA Klonen...........................82
	Hybridisierung von IRS-PCR Produkten der BACs gegen YAC-Klonbanken........................82


IV.	
DISKUSSION................................................................................89

4.1	Genetische Kartierung bei der Maus........................................................89

4.2	Markersysteme.............................................................................90

4.3	Die Beobachtung: Proteinspots eines 2DE-Musters zweier Mausstämmen zeigen Variationen.....92
4.3.1	Sind die Variationen der Proteinspots der Mäusestämme Mus spretus und 
	Mus musculus genetisch bedingt?...........................................................92
4.3.2	Welche Variationstypen wurden gefunden und welchen Erbgängen folgen sie?..................93
4.3.3	Die molekulare Basis von genetischer Variation............................................95
4.3.4	Häufigkeit von Proteinpolymorphismen zwischen zwei Mäusespezies...........................96
4.3.5	Detektierbarkeit von Mutationen mittels 2D-Elektrophorese.................................97
	Quantitative Variabilität der Proteine....................................................99
4.3.6	Praktische Anwendungen: Sind Proteinpolymorphismen als genetische Marker einsetzbar?.....100

4.4	Die Identifizierung kartierter, polymorpher Proteinspots mit MALDI Massenspektrometrie
	enthüllt abweichende Kartierungsergebnisse...............................................101
4.4.1	Die abweichende Kartierung des polymorphen Proteinspots mV147............................102
4.4.2	Die abweichende Kartierung des polymorphen Proteinspots paV410...........................103
	Wie sicher ist unsere Kartierung: besteht Kopplung zu anderen Regionen des Genoms?.......104
4.4.3	Die abweichende Kartierung des polymorphen Proteinspots mV134............................105
	Wie sicher ist unsere Kartierung: besteht Kopplung zu anderen Regionen des Genoms?.......105
4.4.4	Die abweichende Kartierung des polymorphen Proteinspots paV419...........................106
	Wie sicher ist unsere Kartierung: besteht Kopplung zu anderen Regionen des Genoms?.......106
4.4.5	Die abweichende Kartierung des polymorphen Proteinspots aV19.............................108
	Wie sicher ist unsere Kartierung: besteht Kopplung zu anderen Regionen des Genoms?.......108
4.4.6	Die abweichende Kartierung des polymorphen Proteinspots mV82.............................109
4.4.7	Die abweichende Kartierung des polymorphen Proteinspots mV248............................109

4.5	Zusammenfassend: Anwendungen der Proteinkartierungen.....................................110
4.5.1	Neukartierte Proteine als Kandidaten für Krankheitsloci..................................111
4.5.2	Proteinphenotypen - wer verursacht den Phänotyp?.........................................114
4.5.3	Identifizierung von variantem und nichtvariantem Spot des 2D-Gels........................115
4.5.4	Nichtkartierbare Proteinpolymorphismen...................................................117

4.6	Die Biologische Aussage der Kartierung von Interspezies-Polymorphismen...................119
	Der Prozess der Artbildung...............................................................119
	Die Auflösung der genetischen Karte - warum kartieren viele Proteine auf gleiche
	Positionen?..............................................................................120
	Analyse der Spotgruppen identischer, genomischer Position hinsichtlich der Abschätzung
	der Anzahl verschiedener Proteine auf einem 2DE-Gel......................................122

4.7	cDNA-Kartierung - die physikalische Alternative..........................................124

V.Referenzen...............................................................................128


ANHANG

Chromosomenkarten:
Chromosom 1,
 2, 3,
 4, 5,
 6, 7,
 8, 9, 
10, 11,

 12, 13, 
14, 15, 
16, 17, 
18, 19 und X der Maus
Legende zu den Chromosomenkarten

Tabelle1: 
Liste der polymorphen Proteinspost und Varianten in der cytosolischen Fraktion von Maus Gehirn.
Kartierungsposition, Kopplungswahrscheinlichkeiten und genetische Abstände
Legende zu Tabelle 1

Tabelle 2: Liste von polymorphen und nicht-polymorphen Spots, die zur selben Spotfamilien gehören,
jedoch auf mehrere verschiedene Positionen der Mauschromosomen kartieren

Veröffentlichte Arbeiten


More Information:

Online available: http://www.diss.fu-berlin.de/2002/151/indexe.html
Language of PhDThesis: german
Keywords: proteomics, genetic mapping, mouse, two-dimensional electrophoresis, polymorphism, variant
DNB-Sachgruppe: 32 Biologie
Date of disputation: 11-Sep-2001
PhDThesis from: Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin
First Referee: Prof. Dr. Dr. Joachim Klose
Second Referee: Prof. Dr. Ferdinand Hucho
Contact (Author): Christina.M.Nock@gsk.com
Contact (Advisor): klose@charite.de
Date created:12-Aug-2002
Date available:27-Aug-2002

 


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