Vitamin A palmitate have teratogenic effects on the development of neural tube, heart, limbs, genitourinary system, eye, respiratory tract, abdominal wall and skin. In the present study, the injection of developing chick embryos with Vitamin A decreased their survivability compared to control (Fig 1). This is in accordance with previous studies
(Drake et al., 2006, Brand et al., 2008 and
Grant et al., 2018). The chick embryos showed increased mortality when examined 24-72 hours later. Embryos were recovered at days 4, 8 of incubation and newly hatched chicks. Effects of Vitamin A palmitate on embryonic mortality with different doses are summarized in Fig 1.
The percentage of embryonic mortality was observed in egg injected with 15, 30 and 75 IU/ml Vitamin A palmitate decreased significantly with increasing dose respectively compared to the control group. This finding is in accordance with other studies which reveals that there is a significant in the treatment with 75 IU/ml
(Dubey et al., 2018 and
Shukrun et al., 2019). The wet body weight and, crown rump length were recorded and compared with control group and summarized Fig (2 and 3). There were a significant (p>0.05) reduction in both parameters length in all treated groups compared to control group. Our results are coincide with that reported by
(Abbas s et al., 2016; and
Bekhet 2019).
As regards to the qualitative malformations that observed in the treated groups as compared to control groups were summarized in Table 1,2. Such as microcephaly, hydrocephaly, hematoma formation, Omphalocele, microphthalmia, anomalous legs, everted viscera and ectopia cardis and heart and neural defects. Moreover many malformations were appeared in the developing chick embryo as shown in Fig 4 were brain decreased in size and changed in shape (Fig 4 b-f) compared to control group (Fig 4a). In addition to the newly hatching chick ,with haematoma observed in (Fig 4g) ,there were failure to retraction of their yolk sac (Fig 5,YS) , dermatitis (Fig 6,D) accompanied with skin devoid of feathers, (Fig 6NS ) and everted viscera (Fig 7, EV). Nearly all of these malformation obtained by this study results were confirmed by other researchers such as
Farzaneh et al., 2017 and
Reda et al., 2019. Our study record the duplication in the heart (Fig 4e), brain and eye (Fig 4f). Also showed duplication of the neck forming S-shaped (Fig 7, DN) for first time.
Regarding development control genes Daam1, Daam2, Tbx1, Tbx2, Tbx3, Tbx4,Tbx5, Hox3, Hox5, Hox7 and Hox10 expression were analyzed in 5 days , 8 days and 18 days embryo. The expression frame is showed in Fig (8-10). Daam1 and Daam2 expression analysis showed in Fig 8. Daam1 showed a very high expression by the 5
th day and the same expression rate continuing up to 8
th day by examining the rate of expression by 18
th day of incubation the expression rate was decreased. The dose concentration effects is appear in the two high doses. Daam1 and Daam2 control the myocardial growth and differentiation
(Singhvi et al., 2008, Li et al., 2011), so its expression was affected in the early development days and this may explain why vitamin A high doses increase the expression rate in the 5
th and 8
th days embryo (Fig) Vitamin A also affect the expression profile of Daam2 which usually compensate the role of Daam1 one when its expression rate is affected
(Ajima et al., 2015 and
Kannaki et al., 2018). This may explain as it is shown in figure the expression rate of Daam2 in three treatment doses was nearly same Fig 8. Also Daam2 is a modulator for spinal cord development through the increasing of Dvl3/Axin2 clustering inside cells by this way it can promotes Wnt signaling by stabilization of such clusters
(Lee and Deneen 2012). Results of this work showed that Daam1 is more affected than Daam2 and this may be due to the effect of vitamin A on GTP-bound Rho
(Goode and Eck 2007-
Li and Higgs 2005).
In addition, study of five members of Tbx gene (Tbx1, Tbx2, Tbx3, Tbx4 and Tbx5) were examined in this work and results showed a different pattern for each member as shown in Fig 9. Tbx1 expression is affected by high dose of vitamin A. Tbx1 and Tbx5 down regulated by time of incubation and the other three members are fluctuated between upregulation and down regulation. The expression results are in agree with results of
(Esteban et al., 1999) which controlled by the FGF signaling.