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The Pathogenesis of Diseases from The Pathogenesis of Diseases from Genetic and Genomic Point of ViewGenetic and Genomic Point of View

Part 3Part 3 - Nonmendelian - Nonmendelian

©©Oliver Oliver RRácz and František Ništiarácz and František Ništiar

Institute of Pathological PhysiologyInstitute of Pathological Physiology

Medical School, Šafárik UniversityMedical School, Šafárik University

20152015/2016/2016

NONMENDELIAN FORMS OF NONMENDELIAN FORMS OF INHERITANCEINHERITANCE

Expansion of trinucleotideExpansion of trinucleotide repetitions repetitions (dynamic mutations)(dynamic mutations)

ImprintingImprinting Mitochondrial genes and geneticsMitochondrial genes and genetics Errors in alternative splicingErrors in alternative splicing (This chapter is NOT about the inheritance (This chapter is NOT about the inheritance

of complex diseases)of complex diseases)

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Expansion of trinucleotideExpansion of trinucleotide repetitions (dynamic mutations)repetitions (dynamic mutations)

Increased number of triplets (not insertions) Increased number of triplets (not insertions) diseasedisease ??? ???

Increase of repetition number from one generation Increase of repetition number from one generation to the next (anticipation)to the next (anticipation)

Does not fit into our concept of classical genetics, Does not fit into our concept of classical genetics, molecular biology and mutationsmolecular biology and mutations

More repetitions, more severe diseaseMore repetitions, more severe disease Only in humans ???Only in humans ??? Mostly in noncoding regionsMostly in noncoding regions Also in exons, but only CAG = GluAlso in exons, but only CAG = Glu

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DIFFERENT POSSIBILITIES

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Expansion of trinucleotidExpansion of trinucleotid repetitions (dynamic mutations)repetitions (dynamic mutations)

sy. Martin sy. Martin && Bell, mental retardation, X - linked Bell, mental retardation, X - linked

(fragile X, FRAXA) men 1/1000; women 1/2500(fragile X, FRAXA) men 1/1000; women 1/2500– FRAXE, mental retardation (X) less severeFRAXE, mental retardation (X) less severe

– Myotonic dystrophy (m. Steinert, AD)Myotonic dystrophy (m. Steinert, AD)

Huntington disease (AD) ataxia & dementiaHuntington disease (AD) ataxia & dementia– Spinal & bulbar muscular atrophy (AR), Spinal & bulbar muscular atrophy (AR),

spinocerebellar atrophy type 1, Haw River sy, Machado spinocerebellar atrophy type 1, Haw River sy, Machado - Joseph disease (all AD)- Joseph disease (all AD)

Friedreich ataxia (AR)Friedreich ataxia (AR)

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29 29 29 29 29 29 29 29

55 75 95 120 200 325 500

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sy. Martin sy. Martin && Bell, Bell, mental retardation, X - linked mental retardation, X - linked

The second most common cause of mild The second most common cause of mild mentmentaal l retardretardationation (IQ 60 – 20) (IQ 60 – 20)

SSpecific pecific signssigns – elongated – elongated face, big ears, face, big ears, mamaccrorchidirorchidissmm, mitr, mitraall valve valve prolaps prolapsusus

1/1550 m; 1/2500 f1/1550 m; 1/2500 f A fragile region of the long arm of A fragile region of the long arm of X (X (incubation incubation

in sin specipeciaal l medium – without folic acidmedium – without folic acid))

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sy. Martin sy. Martin && Bell Bell Xq27, gene FMR-1, Xq27, gene FMR-1, chromosome breaks, hypermethylationchromosome breaks, hypermethylation CGC repetitions in CGC repetitions in noncoding noncoding 55’’ region region 6 - 53 (mostly 29)6 - 53 (mostly 29) norm, stablenorm, stable 54 - 20054 - 200 „premutation“ expansion„premutation“ expansion 200 - 200 - 44000000 full full mutation, mutation, methylation affects the promotor region (OFF)methylation affects the promotor region (OFF) Asymptomatic men pass the defect to their Asymptomatic men pass the defect to their

daughters, increase of triplet number, daughters, increase of triplet number, manifestation in the next generationmanifestation in the next generation

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sy. Martinsy. Martin & & Bell Bell The coded protein isThe coded protein is FMRP FMRP FuncFuncttiions ofons of FMRP FMRP

– High High expresexpresssiionon in brain andin brain and testes testes– Binds to ribosomes and the complex is Binds to ribosomes and the complex is

transported through axons and dendrites near to transported through axons and dendrites near to synapsessynapses

– Regulates the Regulates the transltranslation of sation of specific pecific proteins of proteins of nervous systemnervous system

Decreased Decreased expresexpresssiionon – ment – mentaal retardl retardationation

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Zero generation

Man, premutation, healthy

First generation

All daughters carriers of permutation, healthy

Sons healthy

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A daughter of first generation

Change to full mutation during oogenesis

Why? How? Always?

SECOND AND FURTHER GENERARIONS

Sons affected with 50% probability

They are fertile!!!

Daughters 50% mild signs

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Group of neurodegenerative Group of neurodegenerative diseases - Huntington diseases - Huntington (+ (+ 77 others) others) Only nervous tissueOnly nervous tissue, death of a specific group of cells; , death of a specific group of cells;

manifestation in early adulthoodmanifestation in early adulthood In Hungtinton In Hungtinton repetitions in exons - > 35 CAG = > 35 Glu repetitions in exons - > 35 CAG = > 35 Glu

in proteinin protein Gain of function mutationsGain of function mutations Lot of unanswered questionsLot of unanswered questions

– why in adulthood ?why in adulthood ?

– why a specific group of cells ?why a specific group of cells ?

the expression of a (mutated) gene depends on a lot the expression of a (mutated) gene depends on a lot of other genes !!!of other genes !!!

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HuntingtonHuntington

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1872 George Huntigton in age 22 years „on chorea“

HuntingtonHuntington ProgresProgressivesive ataxia (chorea) a ataxia (chorea) and decrease of nd decrease of ccognitognitiveive a andnd

mentmentaal funcl functionstions. . Broad scale of symptoms, big individual Broad scale of symptoms, big individual differencesdifferences

Beginning typically in age Beginning typically in age 35 – 44 35 – 44 years, sometimes earlier – years, sometimes earlier – poor prognosispoor prognosis

Heredity is formally Heredity is formally dominantdominant The faulty protein is prone to aggregationThe faulty protein is prone to aggregation The diagnosis of mutated gene is possibleThe diagnosis of mutated gene is possible – a – and thereafter???nd thereafter???

– PoPossitivitivee = = fatefate, negativ, negative =e = „survivor guilt“ „survivor guilt“ Therapy only Therapy only symptomaticsymptomatic

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EpidemiolEpidemiolooggyy

5 – 105 – 10//100 000 (SK 300 – 400)100 000 (SK 300 – 400) Are they Are they diagnosdiagnoseded ? (n ? (not onlyot only HD) HD) ExceptionsExceptions Lake Maracaibo, Venezuela 700/100,000 but also

 Tasmania and some regions in EU An example of „founder effect“ (big families)

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Friedreich ataxiaFriedreich ataxia

Rare AR disease (1/50 000)Rare AR disease (1/50 000) Multisystemic - beside symptoms of Multisystemic - beside symptoms of

nervous system cardiomyopathy and nervous system cardiomyopathy and disorders of glucose metabolismdisorders of glucose metabolism

gene - frataxingene - frataxin repetitions GAA in the 1st intronrepetitions GAA in the 1st intron

– norm 7 - 22, disease 200 - 900 norm 7 - 22, disease 200 - 900 (splicing ???)(splicing ???) Also classic mutations lead to diseaseAlso classic mutations lead to disease

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Imprinting - absolutely against MendelImprinting - absolutely against Mendel

Mendel: Homologous autosomes (mother = Mendel: Homologous autosomes (mother = father) are equivalent (globin father) are equivalent (globin chains) chains)

Imprinting - Imprinting - different expression of genesdifferent expression of genes on on homologous chromosomes (motherhomologous chromosomes (motherfather)father)

Oddity? Prader - Willi & Angelman sy.Oddity? Prader - Willi & Angelman sy. PWS: Muscle hypotony, mental retardation, bulimia - PWS: Muscle hypotony, mental retardation, bulimia -

eat everything what they find, also from garbageeat everything what they find, also from garbage AS: Mental & motor retardation, agressivity, do not AS: Mental & motor retardation, agressivity, do not

sleep („happy puppet syndrome“)sleep („happy puppet syndrome“)

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PWS & AS are different diseasesPWS & AS are different diseases

Caused by deletions of the 15th ch.Caused by deletions of the 15th ch. PWS - deletion on CH15 PWS - deletion on CH15 from fatherfrom father AS - deletion on CH15 AS - deletion on CH15 from motherfrom mother

P PM M

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And this is only the beginning!And this is only the beginning!Uniparental disomyUniparental disomy

P P M M

AS ! PWS !

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Different expression of genes on paternal Different expression of genes on paternal and maternal chromosomesand maternal chromosomes

P M

ABCDE

ABCDE

The same genes are present on both chromosomes

For normal function we needexpression of one set ABCDE

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Different expression of genes on paternal Different expression of genes on paternal and maternal chromosomesand maternal chromosomes

P M

ABCDE

ABCDE

For normal function we needexpression of one set ABCDE

This can be achieved by imprinting(block) of some genes on paternal and maternal chromosome

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ExplanationExplanation

for normal development gene cooperation is for normal development gene cooperation is necessarynecessary

some genes expressed only on maternal, some genes expressed only on maternal, others on paternal chromosomeothers on paternal chromosome

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Deletions of maternal on paternal chromosomeDeletions of maternal on paternal chromosome

ABCDEOK

ACBDE missing

BDEAC missing

Uniparental disomyUniparental disomy

BBDDEEAACC

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ExplanationExplanation

for normal development gene cooperation is for normal development gene cooperation is necessarynecessary

some genes expressed only on maternal, others on some genes expressed only on maternal, others on paternal chromosomepaternal chromosome

AC m +AC m + BDE p = ABCDE BDE p = ABCDE ((O.K.)O.K.) Deletion „m“Deletion „m“ expression BDE not enoughexpression BDE not enough Deletion „p“Deletion „p“expression AC not enoughexpression AC not enough two „p“two „p“ expression BBDDEE not expression BBDDEE not

enoughenough two „m“two „m“ expression AACC not enoughexpression AACC not enough

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MechanismMechanism

methylation of regulatory regions of genesmethylation of regulatory regions of genes catch 22 - what is occuring in the next catch 22 - what is occuring in the next

generation ?generation ?

AC BDEBDE AC

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We should something to do with itWe should something to do with it

SPERMIUM AC & BDE OVUM AC & BDE

& &

PROBLEM WITH THEIR COMBINATION50 % children with PWS or AS

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We should something to do with itWe should something to do with it

SPERMIUM AC & BDE OVUM AC & BDE

& &

Removal of the old sign introduction of new imprinting according to the sex

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We should something to do with itWe should something to do with it

SPERMIUM OVUM

& &

Removal of the old sign introduction of new imprinting according to the sex

FATHER MOTHER

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Parthenogenesis is not workingParthenogenesis is not working

The development of zygotes 46 XX or The development of zygotes 46 XX or 46 XY is normal only when the 46 XY is normal only when the chromosomes are from chromosomes are from both parentsboth parents

Experiments on miceExperiments on mice 46 XX from mother - teratoma46 XX from mother - teratoma 46 XY from father - mola hydatydosa46 XY from father - mola hydatydosa

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Is it really so rare ?Is it really so rare ?

About mice and menAbout mice and men Growth, obesity, energetic metabolismGrowth, obesity, energetic metabolism gene for IGF2 is active paternal CH7 in mousegene for IGF2 is active paternal CH7 in mouse gene for IFG2gene for IFG2 receptor is active on maternal CH17receptor is active on maternal CH17 Pathogenesis of Type 2 diabetes ???Pathogenesis of Type 2 diabetes ??? The cooperation of paternal and maternal part of The cooperation of paternal and maternal part of

genome is not so peacgenome is not so peaceeful ???ful ???

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Mitochondrial Mitochondrial geneticsgenetics In the cells there is In the cells there is oneone nucleus with nucleus with two two

sets of chromosomes (= Mendelsets of chromosomes (= Mendel’s laws)’s laws) In the cells there is a In the cells there is a great number great number ofof

mitochondrimitochondriaa in each of them in each of them more copiesmore copies of circular two-chainof circular two-chain DNA (16569 bp) - DNA (16569 bp) - HETEROPLAHETEROPLASSMIAMIA

MaternMaternaal geneticsl genetics (Ev (Eve from Bible?e from Bible?))

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Functions and pathology Functions and pathology of of mitochondrimitochondriaa

CitrCitraattee cy cyclecle Steroid synthesisSteroid synthesis TerminTerminaal oxidl oxidationation Damaged in hypoxia, repefusion damage Damaged in hypoxia, repefusion damage

(release of free radicals)(release of free radicals) Mitochondria and agingMitochondria and aging

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The sThe strutruccttuurre ofe of mtDNA mtDNA

16959 bp16959 bp Heavy Heavy & Light chain and & Light chain and

D-loop (triple)D-loop (triple) Both chains code genesBoth chains code genes

((withoutwithout intr introonneses)) 13 13 proteinsproteins 2 rRNA2 rRNAss ( (!)!) 22 tRNA22 tRNAss Small noncoding regionsSmall noncoding regions

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Characteristics of mtDNACharacteristics of mtDNA

WithoutWithout hist histoonneses 800 – 1000 800 – 1000 copiescopies ( (upup to to

10 000) in a cell10 000) in a cell Maternal heredityMaternal heredity Higher mutations rate as Higher mutations rate as

in in nDNA (ROS, nDNA (ROS, weakweak reparareparation mechanisms tion mechanisms and also tissue specificityand also tissue specificity

RepliRepliccatatiivvee segreg segregationation

UGA = stop (Trp)UGA = stop (Trp) AUA = Ile (Met)AUA = Ile (Met) AGA/AGG = Arg (stop)AGA/AGG = Arg (stop) RiboRibososommes similar as ines similar as in E.coli E.coli

(chloramfeni(chloramfeniccolol sensitivity sensitivity))

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GGeennes of es of terminterminaal oxidl oxidationation

CCOMPLEXOMPLEX

I. NADH dehydrogenaseI. NADH dehydrogenase II. Succinate II. Succinate

dehydrogenasedehydrogenase III. Ubichinone: III. Ubichinone:

cytochrome C-cytochrome C-oxidoreductaseoxidoreductase

IV. CytochromoxidaseIV. Cytochromoxidase V. ATP synthaseV. ATP synthase

SUBUNBITS IN nDNA SUBUNBITS IN nDNA and mtDNAand mtDNA

I.I. 35 – 735 – 7

II.II. 4 – 04 – 0

III.III. 9 – 19 – 1 IV.IV. 13 – 313 – 3 V.V. 12 – 2 12 – 2

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Mitochondrial diseasesMitochondrial diseases Mutations of mtDNA - nonmendelianMutations of mtDNA - nonmendelian

– Sporadic („somatic“), deletions, duplications, Sporadic („somatic“), deletions, duplications, affecting protein coding genes or tRNAsaffecting protein coding genes or tRNAs

– Maternal („gametic“), point mutations or Maternal („gametic“), point mutations or microdeletionsmicrodeletions

– The combination of both The combination of both (!)(!) Mutations in genes of nDNA coding Mutations in genes of nDNA coding

mitochondrial proteins – mendelianmitochondrial proteins – mendelian Defects of intergenomic signalingDefects of intergenomic signaling

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Mitochondrial diseases (mtDNA)Mitochondrial diseases (mtDNA) Not very common with long namesNot very common with long names

– KSS – Kearns-Sayre syKSS – Kearns-Sayre sy– LHON – Leber hereditary optic neuropathyLHON – Leber hereditary optic neuropathy– MERFF – Myoclonic epilepsy, ragged red fibersMERFF – Myoclonic epilepsy, ragged red fibers– MELAS – Myopathy, encephalopathy, lactic acidosis, apoplexiaMELAS – Myopathy, encephalopathy, lactic acidosis, apoplexia

Mutations in the genes for tRNAs (?!) Mutations in the genes for tRNAs (?!) Forget it – remember only that most of the symptomes Forget it – remember only that most of the symptomes

are consequences of altered energy production in tissues are consequences of altered energy production in tissues with high energy demand – muscles, heart, brain, senseswith high energy demand – muscles, heart, brain, senses

Do not forget it – 22 y. old man with symptoms of Do not forget it – 22 y. old man with symptoms of stroke, CT negative ??? MELAS !stroke, CT negative ??? MELAS !

Accumulation of mutations – explanation of aging?Accumulation of mutations – explanation of aging?