Parental origin impairment of synaptic functions and behaviors in cytoplasmic FMRP interacting protein 1 (Cyfip1) deficient mice

Abstract

CYFIP1 maps to the interval between proximal breakpoint 1 (BP1) and breakpoint 2 (BP2) of chromosomal 15q11-q13 deletions that are implicated in the Angelman (AS) and Prader-Willi syndrome (PWS). There is only one breakpoint (BP3) at the distal end of deletion. CYFIP1 is deleted in AS patients with the larger class I deletion (BP1 to BP3) and the neurological presentations in these patients are more severe than that of patients with class II (BP2 to BP3) deletion. The haploinsufficiency of CYFIP1 is hypothesized to contribute to more severe clinical presentations in class I AS patients. The expression of CYFIP1 is suggested to be bi-allelic in literature but the possibility of parental origin of expression is not completely excluded. We generated and characterized Cyfip1 mutant mice. Homozygous Cyfip1 mice were early embryonic lethal. However, there was a parental origin specific effect between paternal Cyfip1 deficiency (m+/p-) and maternal deficiency (m-/p+) on both synaptic transmissions and behaviors in hippocampal CA1 synapses despite no evidence supporting the parental origin difference for the expression. Both m-/p+ and m+/p- showed the impaired input-output response and paired-pulse facilitation. While the long term-potentiation and group I mGluR mediated long term depression induced by DHPG was not different between Cyfip1 m-/p+ and m+/p- mice, the initial DHPG induced response was significantly enhanced in m-/p+ but not in m+/p- mice. m+/p- but not m-/p+ mice displayed increased freezing in cued fear conditioning and abnormal transitions in zero-maze test. The impaired synaptic transmission and behaviors in haploinsufficiency of Cyfip1 mice provide the evidence supporting the role of CYFIP1 modifying the clinical presentation of class I AS patients and in human neuropsychiatric disorders.

Keywords: Parental origin.

Figure 1

Generation of Cyfip1 1 mutant mice. A. Insertional targeting construct. MICER clone was obtained from MRC. The construct contains an 8.6 kb genomic fragment and 3′ half of Hprt exon, puromycin, and agouti gene marker. Nco1 restriction was used to produce a gap and linearized the genomic DNA before electroporation. B. Cyfip1 targeted allele after insertional event. C. Genotype of Cyfip1 heterozygous mutant mice by genomic Southern blot analysis using 0.6Kb genomic fragment between Nco1 sites as diagramed. D. In m−/p+ and m+p−, the amount of Cyfip1 mRNA relative to WT were different at cortex. *p<0.05.

Figure 2

A&B. Input-Output relationship. A. m−/p+ showed reduced responses than WT at 50, 60 and 100 μA. m+/p− showed reduced responses than WT at 40, 50 μA. C&D. In PPF test, facilitation was increased in m−/p+ than in WT at 100 and 400 ms interstimulus intervals. In m+/p−, facilitation was larger 25, 50 and 100 ms. E&F. DHPG LTD. E. In m−/p+, the DHPG LTD during the last 5 min was not different from WT. The initial slope decrease after DHPG of m−/p+ was larger than WT. F. In m+/p− and WT, DHPG-LTD was not different. G&H. LTP in CA1 with a single high frequency stimulation (100 Hz, 1 sec). No differences in m−/p+ and m+/p− for their WTs. *p<0.05.

Figure 3

A-C Fear conditioning. A. m−/p+ did not differ from WT in contextual or cued test. B. m+/p− and WT were similar in contextual test. In cued test, higher freezing in m+/p− than WT during pretone and tone period. C. Fear conditioning with three electrical shocks in m+/p−. To the tone, m+/p− freezing was higher than WT. D&E. Elevated zero maze. D. m−/p+ did not differ from WT in the time of open arm stay, in the transitions between open and closed arms, or in the incomplete transitions. E. The incomplete transition was fewer in the m+/p− than in WT. F&G. Open field test. The total distance was shorter in m−/p+. *p<0.05. **p<0.01