Daniel Schorderet. Médecin chef Unité d Oculogénétique Hôpital Ophtalmique Jules Gonin, Lausanne

Transcription

1 GENETICS

2 Daniel Schorderet Médecin chef Unité d Oculogénétique Hôpital Ophtalmique Jules Gonin, Lausanne Directeur IRO Institut de recherche en ophtalmologie Av Grand-Champsec 64 Sion daniel.schorderet@irovision.ch daniel.schorderet@epfl.ch

3 Literature - Vogel & Motulsky : Human Genetics problems and approaches, 3rd edition Springer - Levin Genes Oxford University Press Klug & al. Concepts of Genetics. Prentice Hall International editions

4 Genetic q Pedigree drawing q Modes of inheritance - Autosomal dominant - Autosomal recessive - X-linked recessive - X-linked dominant - Mitochondrial - Imprinting - Genomie instability q Risk calculation

5 Look for clinical information Precise diagosis is key to success: Important : - Affected person may have died a long time ago - Individual may have died without a clear diagnosis, with no autopsy - A precise diagnosis may not be possible (then photographies, DNA, fibroblastes, etc. ) - The diagnosis may be wrong! (Carefull in case of indirect analyses ) - look yourself at the patient - look for minor signs in affected and non affected individuals - look for systemic findings - tell patients that many consultations may be needed - additional analysis may be needed - discuss the billing of all the analyses

6 Few symbols used to construct pedigrees Male Female Sex not determined 5 5 individuals with indetermined sex Affected male Deceased female Affected male with no children [ ] Adopted male

7 Few symbols used to construct pedigrees Couple Dizygous twins Consanguineous couple Monozygous twins Couple with daughter Couple with stillbirth

8 Few symbols used to construct pedigrees Family with children Wife separated from the father of her children And divorced from a first marriage Consanguineous family Couple with no children Sterile couple

9 Few symbols used to construct pedigrees I. Pierre Marie II Guy Yvette Albert Jeanne Denis III. 3 Jules Aubin Aristide

10 Few symbols used to construct pedigrees I. Pierre Marie II Guy Yves Albert Jeanne Denis III. 3 Jules Aubin Aristide

11 Few symbols used to construct pedigrees I. Pierre Marie II Guy Yvette Albert Jeanne Denis Cleft lip III. 3 Jules Aubin Aristide right left bilateral

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13 Pedigree : the tools Unaffected? Unknown state Affected (need to define disease) Disease / trait Disease / trait Male with DNA available Index patient

14 Pedigree : what to record For each individual (minimum) First name & last name Date of birth Phone number Disease (affected, carrier, non affected, unknown) DNA obtained? (if yes, DNA #) Informed consent (Y/N) Photographs [Y/N] Date of diagnosis / visit Type of anomalies

15 Pedigree : PROGENY software

16 Pedigree : PROGENY software

17 Pedigree : PROGENY software - database

18 Pedigree : pediro - Pedigree drawing program freely available at

19 Pedigree : first degree relatives I 3 4 II III IV

20 Pedigree : second degree relatives I 3 4 II III IV

21 Types of transmission Mendelian autosomal X-linked dominant recessive Non mendelian imprinting multifactorial other

22 Pedigree I II III IV

23 Dominant inheritance

24 Dominant inheritance : criteria affected individuals in many generations ratio male / female : each affected individual has an affected parent unless : new mutation non penetrance risk for offspring of affected parent: 50% non affected individual doesn t transmit the disease risk of transmission is independent of consanguinity

25 Dominant inheritance Punnett s diagram Affected parent (Aa) Gametes A a Normal parent (aa) Gametes a a Aa aa affected normal Aa aa affected normal

26 Dominant inheritance : non syndrome retinitis pigmentosa Dominant Sporadic Recessive X-linked Hamel et al., JFO 000;3:985

27 I 3 4 II III IV Retinoblastoma Retinoma What type of inheritance??

28 Dominant inheritance I 3 4 II III IV Retinoblastoma Retinoma What type of inheritance??

29 Dominant inheritance I 3 4 II III IV Retinoblastoma Retinoma What type of inheritance??

30 Dominant inheritance : non-penetrance I 3 4 II III IV Retinoblastoma Retinoma What type of inheritance??

31 Dominant inheritance : low high expression I 3 4 II III IV Retinoblastoma Retinoma What type of inheritance??

32 Expressivity

33 Expressivity

34 Dominant inheritance. Phenocopy identical clinical presentation, but different molecular causes. Penetrance number of affected individuals number of mutated individuals 3. Expressivity measure of the gravity of the disease 4. Germline mosaicism A subset of the germline cells is mutated (0 < mosaicism < 0.50)

35 I 3 4 II III IV

36 Recessive inheritance I 3 4 II III IV

37 Recessive inheritance

38 Recessive inheritance : criteria affected individuals in one generation ration male / female = increased risk if consanguinity both parents of an affected child are heterozygous (unless neomutation) recurrence risk: 5% caution: frequency of the carriers

39 Recessive inheritance Punnett s diagram Parent carrier (Aa) Gametes A a Parent carrier (Aa) Gametes A a Aa aa carrier affected AA aa normal carrier : :

40 Dominant inheritance : non syndrome retinitis pigmentosa Dominant Sporadic Recessive X-linked Hamel et al., JFO 000;3:985

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46 Iimportance of consanguineous families for science

47 Transmission?

48 Pseudo-dominance transmission

49 Case report : retinitis pigmentosa I II 3 4 III IV

50 Case report : retinitis pigmentosa I II 3 4 III IV Transmission from one generation to the other Males are more frequently affected No father-to-son transmission

51 X-linked inheritance

52 Case report : retinitis pigmentosa RP Unknown 5 63 RPGR Maubaret et Hamel, JFO 005;8:7

53 X-chromosome Inactivation. Oocyte X active Oocyte X active Zygote X M X P Morula X M X P X active Meiosis Early blastocyste X M X P Preferential Paternal inactivation In the trophectoderm reactivation Oogonia Random inactivation Late blastocyste X M X P / X M X P Random inactivation In the inner mass Permanent inactivation In somatic cells

54 Inactivation de l X : mosaicism in the female LacZ transgene incorporated in one X chromosome

55 X-chromosome Inactivation. Clinical Implications v v Non random Inactivation «spreading» of inactivation in a translocated chromosome

56 I II III

57 X-linked dominant inheritance with lethality in the males I II III Transmission from one generation to the other Lack of males No father-to-son transmission - Incontinentia pigmenti - dystrophy punctata, type - hypophosphatémic rickets - etc.

58 Close-up right wrist with nobble of ulna marked with 4 red circles, his left wrist is probably more representive. Leri-Weil dysostosis

59 Belin et al. Shox mutation in dyschondrosteosis (Leri-Weill). Nat Genet, 998

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61 I 3 4 II III IV Inheritance?

62 Mitochondrial inheritance

63 Mitochondrial inheritance : Leber optic atrophy (LHON) I 3 4 II III IV

64 Mitochondrial DNA Abnornal mitochondriae

65 Mitochondrial DNA : important facts - maternal transmission kb, circular DNA - 37 genes ( RNA ribosomial, trna, 3 subunits OXPHOS) (the 74 other subunits are coded by the nuclear genome) - more than 000 DNA molecules / cells in more than 00 mito) - mature ocytes : > DNA molecules - specific code - non proof reading

66 Leber Hereditary Optic Neuropathy : LHON Acute central vision loss Begin between 0-5 years Optic atrophy Abnormal colour vision Encephalopathy Maternal transmission Incomplete penetrance (50% males, 0% females) 95% of patients have either G3460A, G778A or T4484C

67 Mitochondrial DNA : transmission Homoplasmy/heteroplasmy

68 What type of transmission is it? I II III IV V 3 4 5

69 What type of transmission is it? I II III IV V 3 4 5

70 Imprinting inheritance

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72 Genomic instability

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74 50% 5 < 40

75 > 50 > 000

76 n = pb n = 3 <.5 Kb n = 35 patients.5-3 Kb n = 8 patients Kb n = 7 patients > 4.5 Kb Age [years] N < >60 never

77 n = 3 patients pb n = 3 patients <.5 Kb n = 35 patients.5-3 Kb n = 8 patients Kb n = 7 patients > 4.5 Kb Level special classes repeated class average advanced

78 Diseases due to genomic instability Diagnostic FRAXA (X fragile) FRAXE Huntington SCA SCA SCA3 (Machado Joseph) SCA6 SCA7 SCA8 Steinert disease Friedreich s ataxia Kennedy disease (AR) DRPLA Type CGG CCG CAG CAG CAG CAG CAG CAG CAG CTG GAA CAG CAG Localisation 5 5 Coding Coding Coding Coding Coding Coding Coding 3 Intron Coding Coding

79 Risk calculation Examples

80 Risk calculation : examples Dominant Disease (rétinoblastome) - prob of inheriting the mutation?

81 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance = 80%?

82 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance = 80%?

83 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) of II. if penetrance (p) = 80% I. II.

84 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) of II. if penetrance (p) = 80% I. II. Is one of the parent a non penetrant carrier? Or has II. a new mutation?

85 Risk calculation : examples Dominant Disease (chorea Huntington) - p (of being a carrier) if not affected by the age of 60 years I. II.

86 Risk calculation : examples Recessive Disease (oculo-auricular syndrome)?

87 Risk calculation : examples Recessive Disease (oculo-auricular syndrome)?

88 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II. is carrier

89 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II. is a carrier / x /3 = /3

90 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II.3 is a carrier, with a non affected brother

91 Questions??

92 Risk calculation : examples Dominant Disease (rétinoblastome) - prob of inheriting the mutation? ( ) + µ = If µ is <<

93 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance = 80%? ( ) x penetrance (0.8) = 8 0 = 0.40

94 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance = 80% Probability Condition true Condition not true A priori P(C) P(NC)? Conditionnal P(O C) P(O NC) jointe P(C ) x p(o C) P(NC)x p(o NC) p à posteriori : P(C) x P(O C) P(C ) x p(o C) +P(NC)x p(o NC)

95 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if pénétrance (p) = 80% I. II. Probability II. hetero II. not hetero III.? A priori Conditionnal / / joint

96 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if pénétrance (p) = 80% I. II. Probability II. hetero II. not hetero III.? A priori Conditionnal / -p / joint

97 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if pénétrance (p) = 80% I. II. Probability II. hetero II. not hetero III.? A priori Conditionnal / -p / joint / (-p) / p à posteriori (II. hetero) : -p -p

98 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance (p) = 80% I. II. -p -p III. x -p -p x p

99 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance (p) = 80% I. II. -p -p III. x -p -p x p = p p 4 - p

100 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance (p) = 80% I. II. -p -p = /6 III. x -p -p x p x /6 x 0.8 = p p 4 - p /5

101 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) of II. if penetrance (p) = 80% I. II. p = prob of having a normal allele q = prob of hagin a mutated allele q+q = (p+q) x (p+q) = p^ + pq + q^

102 Risk calculation : examples Dominant Disease (rétinoblastome)

103 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance (p) = 80% I. II. Probability parent hetero No parent hetero A priori Conditionnal parents N clin affected child 4pq -p /p -4pq =~ µp joint 4pq(-p)(/p) µp p a posteriori : 4pq(-p)(/p) 4pq(-p)(/p) + µp = P(H)

104 Risk calculation : examples Dominant Disease (rétinoblastome) - p (of developing the disease) if penetrance (p) = 80% I. Rétinoblastoma II. µ = / p = 0.8 pq = /70 p (affected) =/ x P(H) x p =~.5 / 000

105 Risk calculation : examples Dominant Disease (chorea Huntington) - p (of being a carrier) if not affected by the age of 60 years I. II. p hetero if N 0 ans ans ans ans ans ans % ans

106 Risk calculation : examples Dominant Disease (chorea Huntington) - p (of being a carrier) if not affected by the age of 60 years I. II. Probability II. hetero II. not hetero A priori / / p hetero if N Conditionnal N at 60 years /0 0 y y y y y y 0.05 joint p à posteriori : /0 / /0 /0 + / = / 6 = 0.6

107 Risk calculation : examples Recessive Disease (oculo-auricular syndrome)? x = 4

108 Risk calculation : examples Recessive Disease (oculo-auricular syndrome)? ( ) ( ) x x x 3 5 = 50

109 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II. is carrier Probabilité A priori Conditionnal affected son joint I. carrier 4 µ / µ I. not carrier -4 µ =~ µ µ P à postériori : µ µ + µ = /3

110 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) µ + ν µ + ν (µ+ν) + (µ+ν) => (µ+ν) µ + ν (3/ (µ+ν)) + (µ+ν) => 7/4 (µ+ν) µ+ν) µ = ν µ

111 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II.3 is a carrier, with a non affected brother Probability I. carrier I. not carrier A priori Conditionnal affected son non affected joint

112 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II.3 is a carrier, with a non affected brother Probability A priori Conditionnal affected son non affected joint I. carrier 4 µ / / µ I. not carrier -4 µ =~ µ µ P à postériori : µ µ + µ = /

113 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II.3 is a carrier, with a non affected brother / x / = /4

114 Risk calculation : examples X-lined Disease (RPGR-linked retinitis pigmentosa) Probability that II.3 is a carrier, with a non affected brother / x / = /4 / x /3 = /3