P53-Mediated Repression of the Reprogramming in Cloned Bovine Embryos Through Direct Interaction with HDAC1 and Indirect Interaction with DNMT3A

P53 is a transcriptional activator, regulating growth arrest, DNA repair and apoptosis. We found that the expression level of P53 and the epigenetic profiles were significantly different in bovine somatic cell nuclear transfer embryos from those in vitro fertilization (IVF) embryos. So we inferred that abnormally expression of P53 might contribute to the incomplete reprogramming. Using bovine foetal fibroblasts, we constructed and screened a highly efficient shRNA vector targeting bovine P53 gene and then reconstituted somatic cell nuclear transfer embryos (RNAi-SCNT). The results indicated that expression levels of P53 were downregulated significantly in RNAi-SCNT embryos, and the blastulation rate and the total number of cell increased significantly. Moreover, methylation levels of CpG islands located 5' region of OCT4, NANOG, H19 and IGF2R in RNAi -SCNT embryos were significantly normalized to that IVF embryos, and the methylation levels of genome DNA, H3K9 and H4K5 acetylation levels were also returned to levels similar to the IVF embryos. Differentially expressed genes were identified by microarray, and 28 transcripts were found to be significantly different (> twofolds) in RNAi-SCNT embryos compared to the control nuclear transfer embryos (SCNT). Among the 28 differentially expressed transcripts, just HDAC1 and DNMT3A were closely associated with the epigenetic modifications. Finally, ChIP further showed that P53 might repress the epigenetic reprogramming by regulating HDAC1 directly and DNMT3A indirectly. These findings offer significant references to further elucidate the mechanism of epigenetic reprogramming in SCNT embryos.

Ocular sequelae in extremely premature infants at 5 years of age

OBJECTIVE

To report long-term ophthalmological sequelae in extremely premature infants at 5 years and to determine the relationship between neonatal variables (including retinopathy of prematurity; ROP) and the 5 year ophthalmological outcome of these infants.

METHODOLOGY

The study cohort comprised 84 surviving infants born with a birthweight < 1000 g or gestational age < 28 weeks from June 1985 to December 1989. All infants had an ophthalmological assessment between 34 and 40 weeks post conceptional age to document grade of ROP and were assessed at 5 years of age for fundoscopy, visual acuity, refractive error and ocular mobility.

RESULTS

Of the 84 long-term survivors 69 (82%) were formally assessed at 5 years. Overall, 30 (43%) had some form of ocular disorder. Nineteen (27%) had reduced visual acuity of < 6/6 and three of these were blind. Myopia > -0.5 dioptre was noted in eight (12%), hypermetropia > or = 2.0 dioptre in five (8%), astigmatism in seven (11%) and strabismus was present in nine (14%) of the cohort. There was a significant relationship (P < 0.0001) between the incidence of ocular disorders and ROP. However, even those premature children without ROP had a 31% incidence of ocular disorder at 5 years.

CONCLUSION

Long-term ophthalmological follow-up is recommended in all extremely premature infants regardless of the presence of ROP in the neonatal period.

Predictive value of the Griffiths assessment in extremely low birthweight infants

OBJECTIVE

To assess the relationship between the Griffiths Mental Development Scales at 1 and 3 years and the Stanford-Binet Intelligence Scale (S-B) and Beery Test of Visual-Motor Integration (VMI) at 5 years in extremely low birthweight (ELBW) children.

METHODOLOGY

Prospective study of 45 ELBW infants, without severe neurosensory impairment, cared for in a single Level III neonatal intensive care unit.

RESULTS

At 5 years, 36 (80%) children were of average intelligence, 8 (18%) had borderline intelligence and one was mentally retarded. The Griffiths general quotient (GQ) at 1 year had a weak correlation with the 5 year IQ (corr. coeff. = 0.47), with only 17% of children with a GQ < -1 s.d. at 1 year receiving an IQ < -1 s.d. at 5 years. In contrast, the Griffiths GQ at 3 years correlated strongly with 5 year IQ (corr. coeff. = 0.78). Among those children with a 3 year GQ < -1 s.d., 67% had a 5 year IQ < -1 s.d. and all had a 5 year 1Q < 89. The 3 year hearing and speech subscale correlated strongly with the 5 year S-B verbal comprehension factor (corr. coeff. = 0.753) and the 3 year combined eye/hand co-ordination/performance quotient had a moderate correlation with the S-B non-verbal reasoning factor (corr. coeff. = 0.597) and with the Beery VMI (corr. coeff. = 0.49).

CONCLUSIONS

The 3 year Griffiths GQ is a good predictor of 5 year S-B IQ in ELBW children and can be used to identify children who may benefit from intervention prior to school entry.

Extremely low birthweight infants at 3 years: a developmental profile

This study documents the neurodevelopmental outcome at 3 years of 52 of 55 extremely low birthweight (ELBW) survivors (survival rate 49%) born in a tertiary maternity centre from July 1985 through December 1988, and examines more closely the developmental profile of the neurologically normal survivors. At 3 years, 6 (12%) children had severe neurodevelopmental impairment (severe cerebral palsy, blindness, deafness or a General Quotient (GQ) < 70 on the Griffiths Scales), 11 (21%) had mild to moderate impairment and 35 (67%) had no neurosensory impairment and normal development (GQ > or = 85). Significant risk factors for severe impairment were stage 3 or 4 retinopathy of prematurity (odds ratio [OR] 21.5), treatment with postnatal steroids (OR 21), grade III or IV intraventricular haemorrhage (OR 11) and supplemental oxygen at 'term' (OR 6.4). The developmental profile of the 35 neurologically normal children revealed a significant weakness in eye and hand coordination skills and a relative strength in hearing and speech skills. Early recognition of this developmental profile may allow implementation of more appropriate preschool programmes for ELBW children.