PUBLICATION

What makes a bad egg? Egg transcriptome reveals dysregulation of translational machinery and novel fertility genes important for fertilization

Authors

Cheung, C.T., Nguyen, T.V., Le Cam, A., Patinote, A., Journot, L., Reynes, C., Bobe, J.

ID

ZDB-PUB-190717-2

Date

2019

Source

BMC Genomics 20: 584 (Journal)

Registered Authors

Bobe, Julien

Keywords

Differentially expressed genes, Egg quality, Microarray, Prediction model, Transcriptome, Zebrafish

Datasets

GEO:GSE109073

MeSH Terms

Protein Biosynthesis*
Wnt Signaling Pathway
Gene Expression Regulation*
Ovum/metabolism*
Fertility/genetics*
Real-Time Polymerase Chain Reaction
Animals
Male
Female
Zebrafish
Transcriptome

(all 11)

PubMed

31307377 Full text @ BMC Genomics

Abstract

Background Egg quality can be defined as the egg ability to be fertilized and subsequently develop into a normal embryo. Previous research has shed light on factors that can influence egg quality. Large gaps however remain including a comprehensive view of what makes a bad egg. Initial development of the embryo relies on maternally-inherited molecules, such as transcripts, deposited in the egg during its formation. Bad egg quality is therefore susceptible to be associated with alteration or dysregulation of maternally-inherited transcripts. We performed transcriptome analysis on a large number (N = 136) of zebrafish egg clutches, each clutch being split to monitor developmental success and perform transcriptome analysis in parallel. We aimed at drawing a molecular portrait of the egg in order to characterize the relation between egg transcriptome and developmental success and to subsequently identify new candidate genes involved in fertility.

Results We identified 66 transcript that were differentially abundant in eggs of contrasted phenotype (low or high developmental success). Statistical modeling using partial least squares regression and genetics algorithm demonstrated that gene signatures from transcriptomic data can be used to predict developmental success. The identity and function of differentially expressed genes indicate a major dysregulation of genes of the translational machinery in poor quality eggs. Two genes, otulina and slc29a1a, predominantly expressed in the ovary and dysregulated in poor quality eggs were further investigated using CRISPR/Cas9 mediated genome editing. Mutants of each gene revealed remarkable subfertility whereby the majority of their eggs were unfertilizable. The Wnt pathway appeared to be dysregulated in the otulina mutant-derived eggs.

Conclusions Here we show that egg transcriptome contains molecular signatures, which can be used to predict developmental success. Our results also indicate that poor egg quality in zebrafish is associated with a dysregulation of (i) the translational machinery genes and (ii) novel fertility genes, otulina and slc29a1a, playing an important role for fertilization. Together, our observations highlight the diversity of the possible causes of egg quality defects and reveal mechanisms of maternal origin behind the lack of fertilization and early embryonic failures that can occur under normal reproduction conditions.

Genes / Markers

Figures

Show all Figures

Expression

Gene	Fish	Conditions	Stage	Anatomy	Assay	Figure
cenpx	AB	standard conditions	Long-pec	whole organism	RTPCR	Fig. 2
dvl2	AB	control	1-cell	whole organism	RTPCR	Fig. 5
dvl2	otulina^zf3104	standard conditions	1-cell	whole organism	RTPCR	Fig. 5
lef1	AB	control	1-cell	whole organism	RTPCR	Fig. 5
lef1	otulina^zf3104	standard conditions	1-cell	whole organism	RTPCR	Fig. 5
otulina	otulina^zf3104	standard conditions	1-cell	whole organism	RTPCR	Fig. 3
rpf2	AB	standard conditions	Long-pec	whole organism	RTPCR	Fig. 2
rps27.2	AB	standard conditions	Long-pec	whole organism	RTPCR	Fig. 2
rtn4ip1	AB	standard conditions	Long-pec	whole organism	RTPCR	Fig. 2
slc29a1a	AB	standard conditions	Long-pec	whole organism	RTPCR	Fig. 2

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Phenotype

Fish	Conditions	Stage	Phenotype	Figure
otulina^zf3104	standard conditions	1-cell	whole organism dvl2 expression decreased amount, abnormal	Fig. 5
otulina^zf3104	standard conditions	1-cell	whole organism lef1 expression decreased amount, abnormal	Fig. 5
otulina^zf3104	standard conditions	1-cell	whole organism otulina expression decreased amount, abnormal	Fig. 3
otulina^zf3104	standard conditions	1-cell	whole organism tcf7 expression decreased amount, abnormal	Fig. 5
otulina^zf3104	standard conditions	1-cell	whole organism wnt3a expression decreased amount, abnormal	Fig. 5
otulina^zf3104	standard conditions	Prim-5	developmental process arrested, abnormal	Fig. 3
otulina^zf3104	standard conditions	Prim-5	whole organism viability, abnormal	Fig. 3
slc29a1a^zf3105	standard conditions	1-cell	whole organism slc29a1a expression decreased amount, abnormal	Fig. 3
slc29a1a^zf3105	standard conditions	64-cell	whole organism morphology, abnormal	Fig. 4
slc29a1a^zf3105	standard conditions	Oblong	whole organism morphology, abnormal	Fig. 4

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Mutations / Transgenics

Allele	Construct	Type	Affected Genomic Region
inr10Tg	Tg(ddx4:GFP)	Transgenic Insertion
zf3104		Unknown	otulina
zf3105		Unknown	slc29a1a

Human Disease / Model

Sequence Targeting Reagents

Target	Reagent	Reagent Type
otulina	CRISPR1-otulina	CRISPR
otulina	CRISPR2-otulina	CRISPR
otulina	CRISPR3-otulina	CRISPR
slc29a1a	CRISPR2-slc29a1a	CRISPR
slc29a1a	CRISPR1-slc29a1a	CRISPR
slc29a1a	CRISPR3-slc29a1a	CRISPR

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Fish

Fish
AB
otulina^zf3104
otulina^zf3104; inr10Tg
slc29a1a^zf3105
slc29a1a^zf3105; inr10Tg

Antibodies

Orthology

Engineered Foreign Genes

Marker	Marker Type	Name
GFP	EFG	GFP

Mapping

Cheung et al., 2019 ZDB-PUB-190717-2 PMID:31307377

What makes a bad egg? Egg transcriptome reveals dysregulation of translational machinery and novel fertility genes important for fertilization

Cheung et al., 2019

ZDB-PUB-190717-2
PMID:31307377