A woman in Colombia with a rare genetic mutation recently made the ultimate donation to science.
Aliria Rosa Piedrahita de Villegas carried a rare genetic mutation that had all but guaranteed she would develop Alzheimer's disease in her 40s. But only at age 72 did she experience the first symptoms of it. Her dementia was not terribly advanced when she died from cancer on November 10, a month shy of her 78th birthday, in her daughter's home on a hillside that overlooks the city.
Neurology investigators at the University of Antioquia in Medellín, led by Dr. Francisco Lopera, have followed members of Piedrahita de Villegas' vast extended family for more than 30 years, hoping to unlock the secrets of early onset Alzheimer's disease. In that time, they encountered several outliers, people whose disease developed later than expected, in their 50s or even 60s. But none was as medically remarkable as the woman they all knew as Doña Aliria.
In recent years, Piedrahita de Villegas traveled to Boston, where investigators at Massachusetts General Hospital conducted nuclear imaging studies of her brain as part of an ongoing study of this Colombian family, the largest in the world with genetic early onset Alzheimer's. In Boston, it was discovered that Piedrahita de Villegas had exceptionally large quantities of a protein seen in Alzheimer's — amyloid beta — without much tau, the toxic protein that spreads later in the disease cascade. Something had interrupted the usual degenerative process, leaving her day-to-day functioning relatively preserved.
Last year, researchers at Harvard Medical School and the University of Antioquia published the surprise finding that while Piedrahita de Villegas carried a well-known mutation, unique to Colombia, that causes early onset Alzheimer's, she also carried two copies of another rare mutation that appear to have thwarted the activity of the first one. Since then, investigators worldwide have been studying what is known as the Christchurch mutation, a variant on a gene, APOE, that can affect a person's risk of developing Alzheimer's. Thus far, drugs targeting amyloid beta have disappointed in clinical trials. If the protective effect of Piedrahita de Villegas' double Christchurch mutation can be replicated, a new avenue for desperately needed therapies could open.
A pale, bird-boned woman, Piedrahita de Villegas died of a metastatic melanoma that was discovered only in September. Weeks before she died, she was still cracking jokes and remembering life in a rural hamlet of Angostura, the mountain town where she was born and raised as one of eight siblings. In the early 1970s, she fled Angostura and her abusive husband, moving with her two young daughters, Magaly and Rocío, to the city. There she washed and ironed clothes to support the girls, whose two brothers joined them. Like many families fresh from the mountains, they moved frequently around Medellín's sprawling hillside districts, eventually settling in Barrio Pablo Escobar, a neighbourhood built by the drug kingpin as a public-relations gambit in the 1980s.
Piedrahita de Villegas did not have overly healthy habits that might help her stave off Alzheimer's. She could not resist a good party, her daughters said, and even in recent years she liked to tie one on weekly with her girlfriends. Her sweet and chatty nature endeared her to her neighbours, who on November 20 came out in droves to attend a Mass in her honour.
Her melanoma diagnosis, delayed by the coronavirus pandemic, was an unexpected blow. Her daughters recalled her obsessive daily sweeping of her stoop, which exposed her to the sun.
Piedrahita de Villegas was assigned to palliative care, and nursed by family members who kept her toenails painted, her jewelry adjusted and her face freshly made up — as the relentlessly elegant Piedrahita de Villegas insisted that they do — until the end.
She died in her pajamas at 8:30am on a Tuesday.
'We wanted to donate this brain'
Post-mortem studies to learn how dementia works on the brain have been a pillar of Alzheimer's research since 1906, when Dr. Alois Alzheimer, a German psychiatrist and brain anatomist, shared findings from a patient named Auguste Deter, a woman who became known to science as Auguste D.
When Alzheimer met Deter, she was a deeply disoriented 51-year-old housewife who could not state correctly state what she was eating for lunch. She died at 55 after a severe, progressive dementia that would now be called early onset Alzheimer's disease.
It was what Alzheimer discovered in tissue slides of Deter's brain that distinguished her disease from other dementias he had studied. Microscopic seed-like structures permeated her shrunken brain, along with strange tangles that marked where neurons had died. Later these became known as amyloid plaques and tau tangles, key hallmarks of Alzheimer's disease.
Lopera, head of the neuroscience research group at the University of Antioquia in Medellín, called Piedrahita de Villegas "the Auguste D. of our time," noting that as Deter's brain helped elucidate how damage occurred in early onset Alzheimer's, Piedrahita de Villegas' might help show how that damage could be stopped.
Like most families involved with Lopera's research group, who have lived with early onset Alzheimer's for countless generations and remain eager for a breakthrough, Piedrahita de Villegas' children — two daughters and two sons — had agreed to donate their mother's brain for study when she died. The University of Antioquia now holds some 400 brains, most of them from people who have died with genetic, early onset Alzheimer's.
No one expected to have this brain so soon, and Piedrahita de Villegas would likely have lived much longer if not for her cancer. Her daughter Rocío Villegas-Piedrahita said that her mother was aware that her brain would be donated to science, "and she was fine with it. We even joked that it was the 'golden brain.'"
Rocío Villegas-Piedrahita said it seemed to her that Alzheimer's research — drug research, especially — had stagnated. "The death of my mom, as sad as it is for us, may have opened many doors," she said. Her older sister, Magaly Villegas-Piedrahita, agreed: "We're not selfish. We wanted to donate this brain. We just hope the field can advance."
'This is a historic moment'
The brain bank at the University of Antioquia is staffed by medical faculty, residents and students, who communicate by WhatsApp messages and must be ready to move upon news of a death. Brain tissue deteriorates quickly, and samples must be fixed in preservative or frozen within a few hours to be useful.
On the morning of November 10, Dr. Andrés Villegas, director of the brain bank, solemnly shared news of Piedrahita de Villegas' death with his colleagues. "This is a historic moment," he wrote. The team had not worked with the brain of an extreme outlier before, and it was unclear to Villegas whether other researchers had, either. But Villegas said he was also saddened. Many in the research group had come to regard Piedrahita de Villegas as a friend, and her death from cancer had been painful and premature.
His colleague Dr. David Aguillon, in the meantime, took a taxi to extend condolences to Piedrahita de Villegas' family and receive their final consent papers. Aguillon had cared for Piedrahita de Villegas in recent years and accompanied her on study visits to Boston. During their last trip, in April 2019, when Piedrahita de Villegas was still recovering from a knee surgery, he had pushed her all around the cold and rainy city in a wheelchair, a memory she cherished for what remained of her life.
While they waited for Piedrahita de Villegas' body to arrive, Villegas and the staff messaged each other demands: freezers checked, sterile gloves, iodine, cell culture medium, tissue preservative mixed and ready. The brain bank often sends tissue to its collaborators abroad, and within days samples of Piedrahita de Villegas' brain would be under study in Germany and California, as well as Medellín.
Each brain donation begins not in a hospital mortuary but in a large and well-equipped funeral home. The arrangement allows the researchers to remove the brain and walk it quickly to their dissection lab a block away, after which the family can proceed with a funeral or cremation.
Piedrahita de Villegas' autopsy started at 11:30am, three hours after her death. Villegas' senior team members, Aguillon and Johana Gómez, a biologist, suited up in plastic overalls, masks and face shields, precautions made necessary by the pandemic, while a medical student, Carlos Rueda, stood by taking notes.
The team removed the brain with relative ease, although the process is always intricate, with connective tissue that must be carefully severed. Villegas then extracted from deeper in the skull the pituitary gland and olfactory membrane, structures of interest to Alzheimer's researchers. The group took samples of skin, tumour and vital organs, before leaving the remains of their famous patient, one on whom so many research hopes have been pinned, to be cremated.
Within minutes the group converged again down the street at the brain bank's dissection lab, a room no bigger than a walk-in closet. It was nearly 1pm, and Aguillon placed Piedrahita de Villegas' brain on a scale. It weighed 894 grams, just under two pounds — considerably less than a healthy brain. Rueda began photographing it on a rotating platform used to create a three-dimensional image, while Villegas narrated and Aguillon typed.
Villegas noted that the brain had atrophied in a way that appeared typical for an Alzheimer's patient, and that he saw little evidence of cancer, although it was present in many other organs. The brain's low weight struck Villegas as curious given that Piedrahita de Villegas' symptoms were not yet so advanced; in the months before her death, she still recognised her family and friends, still cooked her own meals and bathed herself, and had no trouble recalling words like "neuroscience" and "coronavirus."
But the truly important findings in an Alzheimer's brain are molecular and microscopic. Using a long, blunt-tipped salmon knife, Villegas set to work dissecting the organ to create tissue samples. Tissue staining, involving techniques not altogether different from those used over a century ago by Alzheimer, will have a lot to say about how Piedrahita de Villegas' disease differed from other cases like it; this procedure would be performed by Villegas and his colleagues in Medellín. In the meantime, the team's collaborators abroad had a long list of requests, and time was running out.
Taped to the wall was an elaborate map of the brain indicating the regions most desirable for single-cell RNA sequencing and electron microscopy. Villegas consulted it every few minutes, leaning in and squinting. He needed a sample from the superior frontal sulcus — but how big? And an anterior orbital gyrus.
At 3:30pm, seven hours post mortem, the Medellín team was still collecting samples. They ran a narrow path: trying to meet the needs of their collaborators without taking so long that they compromised the quality of the tissue. "We're under emergency orders," Villegas said; the couriers would arrive the next day.
A story to be told
Among the things that distinguished Piedrahita de Villegas' case from any other like it was that investigators would have genetic, clinical imaging and now autopsy information to work with: a single case, but with a comprehensive suite of data.
At the University Medical Center Hamburg-Eppendorf in Germany, a neuropathology researcher, Diego Sepulveda-Falla, who has worked with the Medellín group for years, awaited a dozen-odd samples from Piedrahita de Villegas' brain. The key one was a frozen piece of the entorhinal cortex, a pinky-size structure that regulates memory and time perception and the first brain region from which tau begins to spread. Sepulveda-Falla said he would use single-cell RNA sequencing and machine learning to compare samples from Piedrahita de Villegas' brain with those from more than 125 Colombians who had died with the same Alzheimer's-causing mutation.
In Santa Barbara, California, a cell biologist, Ken Kosik, and his team, who recently secured a grant from the National Institutes of Health to study tissue from the Medellín brain bank, awaited further samples. On some, they would perform single-cell RNA sequencing, which can reveal how specific genes are expressed in brain cells. Kosik and his colleagues recently discovered the chemical receptor involved in the spread of tau from cell to cell, a receptor earlier found to interact with the APOE gene, which affects Alzheimer's risk. The sequencing results could shed light on how one of Piedrahita de Villegas's two rare mutations may have acted against the other.
Neither Kosik nor Sepulveda-Falla offered a hypothesis about this brain or what they might find. But it was a matter of scientific due diligence to explore it.
"She was a very important patient; her story made news all over the world," Kosik said. "We learned a lot from her — and now that she's died, it's on us to make sure we give it a careful look."
Written by: Jennie Erin Smith
Photographs by: Federico Rios Escobar
© 2020 THE NEW YORK TIMES
