Developmental disturbances in early life stage mortality (M74) of Baltic salmon fry as studied by changes in gene expression.
BACKGROUND
We have studied alterations of gene expression associated with naturally-occurring early life stage mortality (M74) in Baltic salmon using a cDNA microarray and real time PCR. M74-affected fry have several typical neurological, cardiovascular and pathological symptoms. They are also characterized by low thiamine content and show signs of oxidative stress.


RESULTS
Affected fry can be divided into three major groups with early, intermediate or late onset of mortality. If mortality starts during the first third of the yolk-sac stage, virtually all the responses are compatible with stress, which rapidly leads to the common terminal responses. If death occurs during the second third of the yolk sac stage, the terminal stage is preceded by a decrease in globin gene expression, which leads to internal hypoxia when the animals grow and shift from skin- to gill-breathing. Fry will eventually proceed to the terminal responses. The group developing M74 most slowly appears to compensate for reduced oxygen delivery by downregulation of metabolism, and hence some fry can escape death.


CONCLUSIONS
Our study is the first demonstration of diverse transcriptional responses to a naturally-occurring developmental disturbance. Since many of the genes differentially expressed in M74-fry are evolutionarily conserved, the M74 of Baltic salmon can serve as a model for developmental disturbances and environmental stress responses in vertebrates in general.
Centre of Exellence in Evolutionary Genetics and Physiology, Department of Biology, University of Turku, FI-20014 Turku, Finland. kristiina.vuori@utu.fi
Kristiina A M
KA
Vuori
Heikki
H
Koskinen
Aleksei
A
Krasnov
Paula
P
Koivumäki
Sergey
S
Afanasyev
Pekka J
PJ
Vuorinen
Mikko
M
Nikinmaa
D000818:Animals; D002453:Cell Cycle / Q000235:genetics; D016923:Cell Death / Q000235:genetics; D049109:Cell Proliferation; D020964:Embryo Loss / Q000235:genetics*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D005914:Globins / Q000235:genetics; D006657:Histones / Q000235:genetics; D046228:Microarray Analysis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012474:Salmon / Q000196:embryology* / Q000235:genetics*; D016019:Survival Analysis; D013577:Syndrome
D006657:Histones; D012333:RNA, Messenger; D005914:Globins