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3:  Modes of inheritance and constitutional genetics > 20. Microdeletions/microduplication syndromes  > Flashcards

20. Microdeletions/microduplication syndromes  Flashcards

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Biology 101 flashcards
1
Q

What is the cause of Potocki-Lupski syndrome?

A

Duplication at 17p11.2 encompassing RAI1

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2
Q

How is Potocki-Lupski syndrome inherited?

A

Autosomal dominant, majority of cases are de novo

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3
Q

What is the clinical presentation of Potocki-Lupski syndrome?

A

Neurodevelopmental disorder:
- Dev delay, ID
- Hypotonia, dysphagia
- Communication disorder
- ADHD

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4
Q

Describe the mechanism the leads to the Potocki-Lupski syndrome/Smith-Magenis syndrome duplication/deletion

A

LCRs/segmental duplication on chr17p

NAHR occurs between LCRs flanking RAI1 –> recurrent CNV

Non-recurrent CNVs caused by fork stalling and template switching/microhomology-mediated break-induced replication (FoSTeS/MMBIR)

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5
Q

What is the cause of Smith-Magenis syndrome?

A

Deletion at 17p11.2 encompassing RAI1

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6
Q

What is the clinical presentation of Smith-Magenis syndrome?

A

Coarse facial features, dev delay, ID, failure to thrive, hypotonia

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7
Q

What is the cause of DiGeorge syndrome?

A

22q11.2 deletion

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8
Q

What are the major clinical manifestations of DiGeorge syndrome?

A

Congenital heart disease (Tetrology of Fallot, ventricular septal defect), cleft palate, LD, characteristic facies, hearing loss

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9
Q

What other genes can be impacted by 17q11.2 dels/dups?

A

FLCN - Birt-Hogg-Dube (hereditary cancer syndrome)

PMP22 - HMSN1A/HNPP

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10
Q

What is the main gene deleted in DiGeorge syndrome?

A

TBX1

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11
Q

What is the cause of Williams syndrome?

A

1.5- to 1.8-Mb deletion at 7q11

Mostly de novo

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12
Q

What is the clinical phenotype of Williams syndrome?

A

Mild ID, cardiovascular disease, elfin facial features, connective tissue abnormalities

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13
Q

What is the cause of the BP1-BP2 recurrent microdeletion?

A

15q11.2 deletion due to LCRs/NAHR

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14
Q

What is the clinical phenotype associated with BP1-BP2 microdeletion?

A

Susceptibility locus for neurodevelopment disorders such as dev delay

Low penetrance and variable expressivity

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15
Q

What are the key genes deleted in BP1-BP2 deletions?

A

NIPA1 and NIPA2

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16
Q

Which disorders are caused by deletions between the LCRs at 15q?

A

PWS/AS - deletion of BP1-BP3 or BP2-BP3

17
Q

What is the phenotype of Emmanuel syndrome?

A

Multiple congenital abnormalities - microcephaly, cleft palate, congenital heart defects, kidney abnormalities

Pre- & postnatal growth deficiency

Hypotonia, severe developmental delay

18
Q

What is the phenotype of Pallister-Killian syndrome?

A

Multiple congenital anomalies, seizures, severe developmental delay, macrosomia at birth, deafness, dysmorphic features

19
Q

What causes Emmanuel syndrome?

A

Balanced t(11,22) in parent

Prone to 3:1 tertiary segregation

2x normal 11, 2x normal 22s + der 22 t(11,22)

20
Q

What causes Pallister-Killian syndrome?

A

Supernumary iso(12p)

Mosaic, present in CVS, AF, fibroblasts, not in dividing lymphocytes

Results in tetrasomy of 12p

21
Q

What phenotype is associated with 16p11.2 recurrent deletion?

A

Speech and language disorder, motor coordination difficulties, psychiatric conditions, autistic features, obesity

22
Q

What causes 16p11.2 recurrent deletion?

A

NAHR due to LCRs

23
Q

What is a contiguous gene syndrome?

A

A specific recognisable phenotype resulting from the loss or gain of multiple adjacent genes, some of which are dosage-sensitive

E.g. Williams, DiGeorge

24
Q

What causes CMT1A and HNPP?

A

CMT1A - PMP22 dup at 17p11

HNPP - PMP22 del and 17p11

25
Q

What is the phenotype of CMT1A/HNPP?

A

CMT1A = demyelinating peripheral neuropathy, distal muscle weakness and atrophy, sensory loss, and slow nerve conduction velocity. Pes cavus foot deformity and bilateral foot drop

HNPP = milder, recurrent episodes of numbness, carpal tunnel syndrome, foot drop

26
Q

What is the role of PMP22?

A

Plays a key role in maintaining and developing myelin in Schwann cells that insulate neurons

27
Q

What is the cause of Wolf-Hirschhorn syndrome?

A

Del 4pter

28
Q

What is the phenotype of Wolf-Hirschhorn syndrome?

A

Greek warrior helmet appearance

Growth delay, severe ID, seizures

29
Q

What is the cause of Cri-du-chat syndrome?

A

Del 5pter

30
Q

What is the phenotype of Cri-du-chat syndrome?

A

Cat-like cry, severe ID, microcephaly, hypotonia

3:  Modes of inheritance and constitutional genetics (19 decks)

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