Table 1.

Examples of how MOs in zebrafish have been used to understand the role of a particular gene in developmental toxicology of various chemicals. hpf = hours post fertilization; dpf = days post fertilization. TCDD = 2,3,7,8-tetrachlorodibenzo-p-dioxin; PAH= polycyclic aromatic hydrocarbons; BNF= β-naphthoflavone; ANF= α=naphthoflavone; tBOOH= tert butyl hydroperoxide; tBHQ = tert butyl hydroquinone; PCB = polychlorobiphenyl; MPTP = 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine; FICZ = 6-formylindolo[3,2-b]carbazole; PFOS = perfluorooctane sulfonate.

Gene targeted	Toxicant	Time of Exposure	Toxicant Effect	MO effect on toxicity	Reference
Ahr2	TCDD	3-4 hpf	Pericardial edema at 96 hpf	Protected	24
	PCB-126	8-32 hpf	Pericardial edema at 72 hpf	Protected	33
	FICZ	48-56 hpf	Non-toxic, induction of Cyp1 genes	Decreased gene induction	34
	Tri-cyclic PAHs, crude oil	4-48 hpf	Cardiac dysfunction	No effect	35
	PAHs (pyrene)	4-48 hpf	Cardiac dysfunction	Protected
	PAH (benz[a]ant hracene)	6-48 hpf	Pericardial edema	Protected	36
	PAHs (BNF, ANF)	24-96 hpf	Pericardial edema and truncation of Meckel’s cartilage at 72 and 96 hpf	Protected	21
Ahr1a	PAH (pyrene)	6-96 hpf	Pericardial edema and hepatomegaly at 96 hpf	Protected	35
Cyp1a	PAHs (ANF, BNF)	24-96 hpf	Pericardial edema and truncation of Meckel’s cartilage at 96 hpf	Exacerbated	21
	TCDD	4-5 hpf	Pericardial edema and truncation of Meckel’s cartilage at 72 and 96 hpf	No effect	22
Cyp1b1	PAHs (ANF, BNF)	24-96 hpf	Pericardial edema and truncation of Meckel’s cartilage at 96 hpf	No effect	37
Arnt1	TCDD	3-4 hpf	Pericardial edema at 96 hpf	Protected	38
Arnt2	TCDD	3-4 hpf	Pericardial edema at 96 hpf	No effect	29
Ahrra	TCDD	6 hpf	Pericardial edema at 72 hpf	Exacerbated	17
	-	-	-	Mimics TCDD deformities at 72 hpf	17
Ahrrb	TCDD	6 hpf	Pericardial edema at 72 hpf	Exacerbated	17
p53	PCB 126	5-24 hpf	Cardiac dysmorphogenesis at 72 hpf	No effect	39
Sox9b	-	-	-	Mimics TCDD jaw deformities at 72 hpf	13
R-Spondinl	TCDD	2 dpf	Inhibition of fin regeneration at 2-3 days post amputation (4-5 dpf)	Protected	10
Nrf2	tBOOH	24-96 hpf	Mortality at 96 hpf	Exacerbated	8
	tBHQ	4 dpf	Induction of gstp mRNA	Protected	30
	PFOS	4-96 hpf	Increased detection of reactive oxygen species (ROS) and expression of antioxidant genes	Increased ROS detection with DCF- DA probe; reduced induction of HO-1 gene expression	40
cardiac troponin T	PCB 126	5-24 hpf	Cardiac dysmorphogenesis at 72 hpf	Protected	39
Dopamine transporter (DAT)	MPTP	24-96 hpf	Neurodegeneration at 4 dpf	Protected	41
Cox2	TCDD	24-50 hpf	Mesencephalic blood flow reduced at 50 hpf	Protected	42
thromboxane synthase	TCDD	24-50 hpf	Mesencephalic blood flow reduced at 50 hpf	Protected	42
cereblon (CRBN)	-	-	-	Mimics thalidomide toxicity (Exposure 2- 72 hpf results in reduction in size of otic vesicles at 30 hpf, loss or truncation of pectoral fins at 75 hpf,)	43
Cul4a
PTEN (phosphatase/tensi n homolog)- induced putative kinase (PINKl)	MPTP	1-4 dpf	Reduced swimming activity, loss of TH immunoreactivity in cells in the parvocellular pretectal nucleus	Exacerbated	28