GENETICS

Question 1

Overo lethal white syndrome

Answer 1

Mutation endothelin receptor B
-white coat, blue eyes and aganglionosis
-Fatal
-recessive
–> Paint horse

Question 2

Albinism

Answer 2

lack tyrosinase
-Dominant

Question 3

Curly coat

Answer 3

recessive
–> Percheron, Missouri Fox Trotter / Bashkir

Question 4

WFFS

Answer 4

Mutation PLOD1
-Recessive
-thin dermis, less dermal collagen
-fatal

Question 5

HERDA: Hereditary equine regional dermal asthenia

Answer 5

Exon 1 of Petidyl-propyl cis-trans isomerase B gene:
Different collagen folding
–> Quarter > paint, appaloosa
-Hyperextensible, fragile skin
-<2y
+ heart valve, cornea, joint/tendon
-DNA test
-recessive

Question 6

JEB: junctional epidermolysis bullosa

Answer 6

TYPE 1 = LAMC2
–> French and Belgian draft
= fatal

Type 2 = LAMA3
–> American saddlebred
can treat

Erosions skin, sepsis, abnormal teeth.

Recessive

Question 7

Sarcoid

Answer 7

Genetic susceptible
21% heritable
Polygenic:
ELA genes (Equine leucocyte Ag)

Question 8

Melanoma

Answer 8

Mutation Synthaxin 17. -dominant
+ More MC1R (melanocortin1) - dominant
+ less ASIP (agouti)
GREY horses
–> lippizaner, lusitano, camargue, TB, Arabian, Andalusian

Question 9

MH: Malignant hyperthermia

Answer 9

Exon 46 of Ryanodine receptor 1 gene (RYR1)
Autosomal dominant
QH and paint

Question 10

PSSM1

Answer 10

Mutation GYS1: glycogen synthase (abnormal high activity)
–> °increased amylase resistent polysaccharide in skeletal muscle
-Autosomal dominant
–> Quarter (halter), WB, draft horse (not shire, clydesdale)

Question 11

SCID

Answer 11

= lack of DNA proteine kinase
ARABIAN
Lack of adaptive IR (B and T lymphocytes)
Lethal <5m
Typical: Lymphopenia / NO IgM or IgG
–> genetic test exist

Question 12

Foal immunodeficiency syndrome

Answer 12

= SLA5A3 : Na-myoinositol cotransporter
–> vnl Fell and dale ponies
Typical: ANEMIA
NO B-lymphocytes –> LOW IgG
Lethal around 3m

Question 13

CVID

Answer 13

= B-cell depletion –> inadequate Ab production
–> recurrent infections and fever in ADULT horses

Associated genes:
-PAX5
-E2A

Diagnosis:
-HYPOGAMMAglobulinemia
-lymphopenia
-IgG <1000 g/dL
-IgM < 25 mg/dL

Often euthanized within 6 months

Question 14

Lavender foal syndrome

Answer 14

Egyptian arabian > arabian.
MYO5A gene
* Silver / pink pale / lavender colour coat
(disruption melanosome transport to keratinocytes)
* Improper transport of secretory granules in neurons –> neurological abnormalities
-homozygous recessive
-lethal

Question 15

Cerebellar abiotrophy

Answer 15

ECA2 gene
arabian
autosomal recessive
intention tremor, absent menace, ataxia
start 6w-6m