Chinese researchers have mapped the world's first complete spatiotemporal gene expression atlas of human embryos during the critical organ-forming period from four to eight weeks post-fertilization, allowing scientists to move beyond localized observations to a comprehensive, dynamic molecular study of early organ development.

Such advancements will also offer a comprehensive molecular reference for identifying the origins of congenital diseases, said researchers.

A paper about the study jointly conducted by Fudan University in Shanghai, Zhejiang University in Hangzhou city, Zhejiang province, and BGI Life Science Research Institution based in Shenzhen city, Guangdong province, was published on the website of the journal Nature recently.

Experts explained that the four to eight-week period after fertilization marks a crucial phase in embryonic development, but has long been considered a research blind spot due to the challenges in cultivating embryos at this stage and the inability to obtain precise developmental data through imaging.

Gene regulation during this phase determines the trajectory of human development, with errors in this stage potentially leading to congenital heart defects, neurological developmental defects, and other conditions. Previous gene sequencing technologies have been limited, lacking coherent, complete data for this critical period, they said.

Analyzing 13 human embryo samples, the study looked into 50 human organs or anatomical regions and 198 substructures. It fully reconstructed the formation process of organs, including heart, brain, liver, kidneys and skeleton, addressing core scientific questions about which cells appear at which specific times and locations and what regulatory factors drive them.

In a detailed examination of the heart's pacemaker region, the study identified two previously unknown critical genes, RORA and KIAA1324L. Functional experiments in zebrafish and mice confirmed their essential role in pacemaker cell differentiation and heart rate maintenance, offering a new research direction for congenital arrhythmia.

The study also refined the early-stage brain gene region map, discovering that neuron growth occurs earlier than had been traditionally believed, which was described as a textbook-changing discovery by Huang Hefeng, a lead scientist on the research team.

"In the study, we also identified gene regulatory networks related to intellectual development anomalies, providing new insights into the molecular basis to understand neurodevelopmental disorders," said Huang, a renowned expert in reproductive medicine and member of the Chinese Academy of Sciences.

"Additionally, the research mapped the spatiotemporal distribution of receptors for various viruses within the embryo, explaining the susceptibility of different organs to viral infections at various pregnancy stages, which holds significant clinical potentials," she said.

Jiang Hua, director of the Obstetrics and Gynecology Hospital of Fudan University, likened the study to a high-precision navigation map, providing crucial molecular coordinates for understanding early-stage organ development in the embryo and congenital disease origins. It will also contribute to optimizing early pregnancy monitoring, he said.

"As one reviewer of the paper noted, this work is 'a masterpiece eagerly awaited by scientists and clinicians worldwide'," Jiang added.

"It will facilitate humanity to gradually unveil the mysteries of its own life development, advancing life research from structural to molecular, from fragmented to holistic," he said.