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WP - C Data analysis tools Marco Bink & Gerrit Gort

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Page 1: Data analysis tools and associated scientific developments

WP - C Data analysis tools

Marco Bink & Gerrit Gort

Page 2: Data analysis tools and associated scientific developments

Outline

Overview Work Package C C1:Upgrade standard tools

• Partly presented by M. Frisch, HOH

C2: Novel map-based tools C3: Genome-wide and locus specific tools C4: Large-data mining tools C5: Germplasm Simulator

• Presented by M. Frisch, HOH

Concluding remarks

Page 3: Data analysis tools and associated scientific developments

WP-C I Upgrading statistical analysis tools

Objective: Upgrade standard cluster and correlation tools, able to handle large data sets

Case: cluster analysis in S-Plus clustering based on (genetic) distance matrix S-Plus functions not sufficient for large data sets

• May depend on computer capacity

BigClus algorithm (Gerrit Gort PRI) • Written in C-code, accessible in S-Plus via dynamic link library (DLL)

Page 4: Data analysis tools and associated scientific developments

WP-C I BigClus algorithm characteristics

Methods of Clustering Single link Complete link Average link McQuitty’s Ward’s

Distance measures Eucledian Jaccard

Allow missing values Jaccard

Page 5: Data analysis tools and associated scientific developments

Large datasets Ordinary dendograms will not suffice

(e.g., 5000 plants, 100 markers, Jaccard distance, UPGMA)

Ability to look at part of dendogram e.g. show first 25 clusters from top,

show number of observations below each leave.

S-PLUS functions to plot top of tree, plot summary

information on tree, like frequencies, cluster averages of covariates.

WP-C I Dendrograms (from BigClus)

Page 6: Data analysis tools and associated scientific developments

WP-C II Novel map-based tools

Two important issues Account for genetic linkage map information

Consider molecular markers to be dependent variables Combine information from (a) trait characteristics

(b) passport data and (c) molecular markers Map-based diversity tools, cluster & correlation

analysis software

Core - selection

Page 7: Data analysis tools and associated scientific developments

WP-C II Account for genetic linkage maps

Unlinked markers

Loosely linked markers

closely linked markers

Genetic distances Rational: Data on genetic

markers are likely correlated due to underlying genetic map

Utilise correlation structure? Account for correlation!

• Allow different weights for markers

Unequal distribution of markers across genome

Page 8: Data analysis tools and associated scientific developments

WP-C II Account for genetic linkage maps

Correlation among linked markers: erodes with increasing number of meioses separating

two individuals due to recombination increases due to linkage disequilibrium (non-random

mating / selection pressure)

Use all available markers calculate weights for every marker locus

• Partial regression coefficients (Zeng, PNAS ’93)• Meioses factor (Mf,) = Expected average number of meioses

separating two individuals

Page 9: Data analysis tools and associated scientific developments

WP-C II Account for genetic linkage maps

Unlinked markers

Loosely linked markers

closely linked markers

W = 1.0

W = 1.0

W = 0.5

W = 0.7

W = 0.2

W = 0.3

Meff = 5.0

Meff = 2.9

Meff = 1.2

Example!

Page 10: Data analysis tools and associated scientific developments

WP-C II Combine passport, trait & marker info

S-Plus software offers a very limited possibility to combine different types of data Function “Daisy()” applies normalization to all data

variables, no specification of weights across variables

Improve/extend function “Daisy()” Allow user-defined weights for every variable S-Plus function WeightedDaisy()

• E.g., use weights for markers (from S-Plus function WeightMap() )

Page 11: Data analysis tools and associated scientific developments

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phenotypes

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Poor distinction

Poor distinctionFair distinction

WP-C II Multiple sources of data for cluster analysis

Page 12: Data analysis tools and associated scientific developments

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Standard weights (daisy())

User-defined weights (weighteddaisy())

WP-C II Combining multiple sources of data

Page 13: Data analysis tools and associated scientific developments

WP-C II Example marker weights

m0444.8m0547.3

m10113.3

m13151.4

1

m1530.2m1635.6

m1860.7

m1970.2

m2092.5

m22111.3

m23131.2

m24141.5

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m5887.7m5990.9m60100.1m61100.2m62101.4

5

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m7445.9m7548.5m7661.2m7770.5m7871.1m7972.5m8073.8

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9

1.00

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0. 431.00

Page 14: Data analysis tools and associated scientific developments

WP-C II Results of cluster analyses w. & w/out weights1

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Page 15: Data analysis tools and associated scientific developments

WP-C II (next step) Core Selection Form N (e.g., 6) distinct groups

cluster analysis tree Cut tree at arbitrary level Our example: group sizes

• No weights: 81, 7, 6, 2, 2, and 2

• Map-based weights: 4, 7, 81, 2, 4, and 2

Sample/select from each group a given number Define core selection, e.g., 12 Sampling strategy Standard Map-based

• Constant [2 2 2 2 2 2] [2 2 2 2 2 2]

• Proportional [7 1 1 1 1 1] [1 1 7 1 1 1]

• Logproportional [5 2 2 1 1 1] [1 2 5 1 2 1]

Page 16: Data analysis tools and associated scientific developments

WP-C II Core selection (logproportional sampling)

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12 accessions selected from 6 clusters

Tree from map-based clustering

Page 17: Data analysis tools and associated scientific developments

WP-C III Genome-wide and Locus-specific

mapping

Objective was to develop novel map-based tools for searching systematically for useful genes and alleles in germplasm collections

Genome-wide search

Tagged loci search (fine mapping)

Page 18: Data analysis tools and associated scientific developments

WP-C III Genome-wide mapping

Marker-marker association Assemble genome wide map of AFLP markers (no map available) Only few markers could be mapped last summer (KeyGene) Are high associations indicative for distance between markers on

genome?

Marker-trait association More interesting to associate markers to traits, e.g. Bremia

resistance to map genes coding for trait But: if high associations between markers are not indicative for

distance between markers does it make sense to associate markers to traits then?

Page 19: Data analysis tools and associated scientific developments

WP-C III Retrieval of linkage map from

genome wide pair-wise marker associations

Multi Dimensional Scaling (MDS) One-dimensional representation of markers from pair-

wise distances is achieved, corresponding to a marker map.

Correction for population structure is very important• Logistic regression correction by stratification

Three types of MDS (S-PLUS) evaluated• Classical (= PCO = Principal Coordinate Analysis)

• Kruskal's ( = non-metric MDS)

• Sammon’s MDS ( minimizes weighted “stress”) (performs best)

Page 20: Data analysis tools and associated scientific developments

WP-C III Example MDS to form linkage map

Page 21: Data analysis tools and associated scientific developments

WP-C III Resolution of QTL (fine) mapping

Experiments of linkage analysis 2 or 3 generations of individuals limited number of meioses in experiment dense marker maps hardly improve map-resolution QTL

• Even with RIL populations: 5 - 10 centiMorgan

Higher resolution desired to allow better (molecular) study of gene involved

• cloning, comparative mapping, etc.

identify tightly linked markers• more efficient marker-assisted breeding

Page 22: Data analysis tools and associated scientific developments

WP-C III Locus specific (Fine) mapping

This leads to the detection of a small region containing the disease gene.

Key-paper: Meuwissen & Goddard (2000) Genetics 155:421-430

Linkage disequilibrium mapping successful in mapping genetic disorders:

= Identify a chromosomal region that is identical by descent (IBD)

among diseased individuals (region may contain disease gene)

The IBD region is detected by closely linked marker loci that carry identical alleles at this region in the diseased individuals.

Size of IBD region decreases with the number of meioses since the disease mutation occurred and may be small.

Page 23: Data analysis tools and associated scientific developments

WP-C III Methodology LD fine-mapping of QTL

QTL position known up to 5 - 20 cM precision effective population size for many discrete generations phenotypes available for last generation of individuals Fully inbred individuals (selfed by single seed descent)

(1) Expected correlation matrix among marker haplotypes Whether two marker haplotypes have identical alleles in a region

depends on the position of the QTL. Hence, the covariance between haplotype effects depends on the position of the QTL.

Identity By Descent (IBD) probability (2) Maximum Likelihood estimation of QTL position

Linear model (phenotypes normally distributed) ML estimates for each marker interval

Page 24: Data analysis tools and associated scientific developments
Page 25: Data analysis tools and associated scientific developments

WP-C III Calculate power of QTL fine-mapping 20 markers = 19 intervals

• Simulation: QTL between marker 10 and 11

• Estimated interval: Interval with highest ML estimate

– MLbase = ML without QTL

– MLQTL,I = ML with QTL in interval I

– Test statistic : MLQTL,I - MLbase

Deviations of estimated interval from true interval• -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Power % replicates in true or next to true interval (interval -1 , 0, 1)

1000 replicates/scenario

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Page 26: Data analysis tools and associated scientific developments

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Page 27: Data analysis tools and associated scientific developments

WP-C III Locus-specific search

Separate modules (C–language) for Calculation of IBD probabilities (= expected correlation

matrix) Simulation of data sets & Max. Likelihood estimation

Paper on methodology and simulation results Bink & Meuwissen (2004) Euphytica, in press

Page 28: Data analysis tools and associated scientific developments

WP-C IV Large-data mining tools

Objective was to find important patterns within the germplasm data set, which are not apparent from visual analysis and to compare and contrast these patterns with those found from the classical statistical analyses

Page 29: Data analysis tools and associated scientific developments

WP-C IV Large-data mining tools

Methods Data Mining methods (JIC)

• Decision Trees, Built with C4.5 (Quinlan) [ DAM ]

• Rule induction, Simulated Annealing: Witness Miner 2001

Artificial Neural Networks (PRI)• Linear Vector Quantisation [ LVQ ]

• Support Vector Machines [ SVM ]

(Classical) Statistical analysis (PRI)• LDA/Linear Regression [ CS ]

Page 30: Data analysis tools and associated scientific developments

WP-C IV Large-data mining ‘data set’

Data: 1423 Lactuca Sativa accessions, CGN X1: 167 AFLP markers X2: 20 (2x10) STMS markers Y: 5 traits, all treated as categorical variables

• Y1:[n=1413] seed colour (black, white, varied)• Y2:[n= 761] flowering time (< 41 d., 41-60, …. 101-120 d.)• Y3:[n=1208] leaf colour (yellow, green, grey, blue, red)• Y4:[n= 927] resistance to Bremia 1 (resistant, susceptible)• Y5:[n= 919] resistance to Bremia 3 (resistant, susceptible)

Data split into training and test sample (50 - 50) Objective: use X to predict Y

Page 31: Data analysis tools and associated scientific developments

Criteria: coverage, accuracy, applicability

Rule:

Reality:

A B Tot Cov

A 10 20 30 10/30

B 0 20 20 20/20

Tot 10 40 50

Accur 10/10 20/40

Applic 10/50 40/50A

Page 32: Data analysis tools and associated scientific developments

Results: Resistance to Bremia 1

Performance across all traits: LVQ lowest CS good SVM & DAM best

Note: differences not very large!

Trade-off between increase accuracy and maintain coverage/applicability!

Page 33: Data analysis tools and associated scientific developments

Concluding remarksNovel statistical tools available

Answer questions you could not answer before?

Applicability & integration with other WP–tools

© Wageningen UR