Photograph from 7.01SC Fundamentals of Biology. An illustration showing the double helix structure of DNA (Image courtesy of the National Human Genome Research Institute).

How Do Cells Organize Themselves Into a Heart or a Brain?

Portrait of Hazel Sive

By MIT OpenCourseWare

Ask MIT’s Hazel Sive, an expert in developmental biology, about her work in embryonic development, and her love for teaching immediately shines through. She’s just as likely to start talking to you about music.

“Embryonic development has its own tempo—from the thumping rock beat of early cell division to something more like modern minimalism, where you have cells working together while still doing their own thing, making the music more melodious and complex. Finally, as nerves start working and sending impulses, it moves to something more syncopated and rhythmic.”

Sive has been teaching at MIT since 1991 and is currently Associate Dean of the School of Science and Member of the Whitehead Institute, where she runs her own lab. Her multidisciplinary work, combining genetics, molecular biology, and brain imaging, is highly regarded worldwide for opening exciting new pathways in biomedical research. She has been a pioneer in the study of the vertebrate embryo, with a focus on the various signaling systems that determine how cells differentiate into specific organs.

A Teacher Who Can Teach Anyone Anything

As a child growing up in South Africa, Sive showed an early curiosity for the sciences, and credits her father as a major influence: “He was an inventor—an electrical engineer. I remember him working in his shop, designing switching devices or circuits that he would sell to the telephone company,” she recalls. “I was always welcome in his shop. For me, as a child, it was a wonderful place to explore. He allowed me to use absolutely anything, his band saw, his tools, anything,” she jokes.

Yet her love for the lush coastal landscape of South Africa, and “digging in the garden for all sorts of crawly, jumping things,” eventually led Sive into the life sciences. Her high school science teacher noticed Sive’s aptitude for science.

“She was a very serious teacher. I think if she saw that you were interested, she paid extra attention to you. I remember how she once took me aside in lab and taught me how to properly use a burette. She said, ‘You’re going to study science in university someday, so you better learn to use this thing properly.’ That really meant a lot to me, that kind of attention.”

Although Sive admits that she had only a vague idea where her studies would actually lead her, she held on to two goals as an undergraduate—either to become a veterinarian and fight for animal rights, or to study ecology and politics and work to preserve the South African environment. Growing political tensions in apartheid South Africa, however, led her to make the difficult decision to leave for England after completing a double major in zoology and chemistry at the University of Witwatersrand in Johannesburg.

At the time, England’s public high schools were short of qualified science teachers: “It meant that as a chemistry-zoology double major, they were ready to let me teach practically anything, even without a teacher’s diploma. But it was trial by fire, and all very challenging. I was only 21 and at one point they had me teaching A-level boys who were sometimes as old as 19.”

“Two weeks later I received a teaching diploma from the government, which meant I could teach anywhere in England. I suppose they felt that someone who could successfully teach 60 kids about fractions could teach anyone anything.”

From those days in England, she recalls one of the proudest moments in her early teaching career. “On one particular day, I had sixty pre-teen boys in my class and my job was to teach them something about fractions—not such an exciting lesson. A gentleman in a suit asked if he could observe, and I told him that if he could find a seat, he was welcome to stay.

By the end of the hour, I’d managed to cover my lesson, and the gentleman left without a word. Two weeks later I received a teaching diploma from the government, which meant I could teach anywhere in England. I suppose they felt that someone who could successfully teach 60 kids about fractions could teach anyone anything.”

A Different Style of Thinking

Teaching remains a core focus of Sive’s professional life and a clear source of enjoyment and inspiration to her. She teaches an introductory biology course to incoming first-year students every year, and she loves how the students constantly challenge her with new questions that she’s never considered.

She remarks admiringly how, in recent years, students have acquired a more sophisticated molecular vocabulary, thanks to the increased presence of molecular biology in the high school curriculum.

“When I ask students how cells know to build a heart, they talk about active and inactive genes, and signaling pathways. It’s a different style of thinking, a different approach. Students use a very different vocabulary than I might have encountered even five years ago.”

It’s a vocabulary that Sive’s research continues to enrich. Her undergraduate studies, doctoral studies at Rockefeller University, and postdoctoral studies at the Fred Hutchinson Cancer Center influenced the three major pursuits of the Sive Lab at the Whitehead Institute. The first is trying to better understand why the brain forms in a tubular shape, and what specific properties and advantages that brings to vertebrates.

The second is gaining an understanding of how the various features of a face form and organize themselves at a cellular level. Lastly, she studies the early development of the zebrafish nervous system as a means to better understand how genetic mutations can cause human mental health disorders.

Hazel Sive’s early and ardent support of OCW is a perfect reflection of her firm belief in the importance of science and education in advancing society today.

OCW Courses Taught by Professor Sive