TMEM167A and MEDS Syndrome in Neonatal Diabetes

When diabetes emerges during the first weeks of life, doctors look for more than an underlying problem with blood sugar.

Paediatric specialists now monitor these uncommon cases closely, as advances in genetics and cell biology reveal why certain newborns develop diabetes alongside serious neurological symptoms within days of being born.

A rare neonatal diabetes linked to deeper problems

Neonatal diabetes develops during the first six months of life and can appear only hours after birth. Although uncommon, it is seldom subtle. Parents may see poor feeding, dehydration, weight loss or even coma. Clinicians usually need to bring blood glucose under control urgently before the underlying cause is clear.

In most affected infants, the cause is written into their DNA. Variants in genes responsible for insulin production or release prevent pancreatic beta cells from functioning properly. This alone creates a lifelong health challenge. However, in a particularly concerning group of babies, diabetes is only one feature of a broader syndrome that also affects the brain.

Some infants with neonatal diabetes experience seizures, pronounced microcephaly (a substantially smaller head size) and developmental delay. This cluster of features is now known as MEDS syndrome, meaning “microcephaly, epilepsy and neonatal diabetes syndrome”. The disorder is exceptionally rare, but has attracted major interest because it connects two organs usually managed as separate concerns: the brain and the pancreas.

MEDS syndrome suggests that a single molecular fault can derail both brain development and insulin production before birth.

For many years, researchers identified only two principal genetic causes of MEDS: variants in IER3IP1 and YIPF5. Both genes are involved in intracellular trafficking, the network of miniature transport pathways that shifts proteins around cells. If these routes malfunction, beta cells cannot effectively process and release insulin, while developing neurons struggle to grow and form appropriate connections.

TMEM167A emerges as a key gene

In 2025, a European research consortium introduced a third gene into this picture: TMEM167A. After sequencing the genomes of six unrelated children with neonatal diabetes, microcephaly and, in most instances, epilepsy, researchers found recessive TMEM167A variants in every child. Before this study, the gene had received limited attention.

Recessive inheritance means that disease develops only when both gene copies - one inherited from each parent - are faulty. Parents frequently carry one unaffected, silent copy and have no symptoms themselves. This inheritance pattern can make such disorders difficult to anticipate without genetic screening, particularly where there is no recognised family history of neonatal diabetes.

TMEM167A activity in the body

To establish the importance of TMEM167A, scientists examined where and when the gene becomes active during embryonic development. Human tissue samples and sophisticated imaging showed substantial TMEM167A activity in two developing organs: the brain and pancreas.

Within the brain, TMEM167A seems particularly active in areas that generate new neurons, including the pallium, a precursor to the cerebral cortex, and the basal ganglia. Organoids - small brain-like structures produced from stem cells in laboratories - helped to refine this finding. Expression of TMEM167A was stronger in neural stem cells than in fully differentiated neurons.

The gene seems most active in cells that are still building themselves, shaping how both brain tissue and pancreatic tissue take form.

A comparable pattern was seen in the embryonic pancreas. TMEM167A appeared in early progenitor cells and developing endocrine cells, including the beta cells that later make insulin. The gene was present alongside established insulin markers, positioning it centrally in pancreatic development.

Its presence in both organs reinforced the theory that one disrupted pathway can account for both diabetes and neurological symptoms. Instead of two unrelated illnesses coincidentally occurring in one child, a single developmental defect seems to affect both organs.

Inside TMEM167A cells: a protein traffic jam

So what is TMEM167A’s function? The latest research indicates that it has a vital role in intracellular transport, specifically movement between the endoplasmic reticulum (ER) and the Golgi apparatus, the cell’s centres for processing and dispatching proteins.

The researchers created human stem cells containing one of the TMEM167A variants identified in the affected children. They then directed these cells to become pancreatic beta-like cells. Microscopy and biochemical analysis revealed a striking defect: proteins were no longer transported correctly from the ER to the Golgi.

This transport route is essential for proinsulin, insulin’s precursor molecule. Proinsulin folds and matures while travelling through these cellular compartments. If the route fails, proinsulin builds up, misfolded proteins accumulate and stress rises within the cell.

Defective TMEM167A traps proinsulin in a cellular bottleneck, lowering insulin output and making beta cells more vulnerable to stress and death.

The stressed beta-like cells made much less insulin and displayed evidence of early cell death. Once transplanted into mice, they did not release insulin even after stimulation by the researchers, confirming that this was not merely a laboratory artefact.

Potential routes towards future therapies

While the underlying gene variant remains, scientists investigated whether the stress affecting these vulnerable cells could at least be reduced. Two compounds, exendin-4 and imeglimin, provided partial benefit. Both are already recognised in diabetes research, though for different purposes.

• Exendin-4 imitates GLP‑1, a hormone that increases insulin secretion and helps beta cells survive.
• Imeglimin acts on mitochondrial function and energy metabolism in beta cells.

In cells with TMEM167A variants, these compounds lowered markers of cellular stress and improved survival. They did not completely restore cell function, but suggested that medicines targeting internal trafficking pathways could help certain patients preserve more of their own beta cells for longer.

This targeted strategy differs greatly from the insulin injections most commonly associated with diabetes treatment. Genetic neonatal diabetes may eventually be treated according to the precise molecular defect involved. At present, however, the principal impact of the work is on how clinicians understand these cases.

Why neurological symptoms matter in diabetes care

MEDS syndrome is a reminder to paediatricians that diabetes beginning very early in life can indicate a far broader developmental problem. When a newborn or very young infant has high blood glucose, teams now assess carefully for:

• Microcephaly or atypical patterns of head growth
• Early seizures or unusual movements
• Feeding problems not explained by glucose levels
• Delayed developmental milestones during the first months

Recognising this pattern early can prompt genetic testing, parental counselling and more detailed neurological monitoring. It also gives families clearer information about likely future requirements, including speech therapy, physiotherapy and specialist educational support.

The new genetic finding can also affect reproductive decisions. Testing relatives in affected families for carrier status helps them understand the likelihood of another child having the same syndrome. In certain countries, prenatal testing or preimplantation genetic diagnosis may be considered with couples at high risk.

TMEM167A alongside other neonatal diabetes genes

The range of known genetic causes of neonatal diabetes continues to expand. TMEM167A now sits alongside KCNJ11, ABCC8, INS, IER3IP1 and YIPF5, with each gene having a distinct mechanism and clinical presentation. Some mainly affect beta-cell ion channels, whereas others interfere with insulin folding or protein trafficking.

Gene	Main organ affected	Typical features
KCNJ11 / ABCC8	Pancreas	Neonatal diabetes, sometimes controlled with oral sulfonylureas
INS	Pancreas	Insulin misfolding, beta cell loss
IER3IP1 / YIPF5	Brain and pancreas	Neonatal diabetes with microcephaly and epilepsy
TMEM167A	Brain and pancreas	MEDS syndrome: neonatal diabetes, microcephaly, frequent epilepsy

Identifying the responsible gene alters both prognosis and possible treatment. Some children with KCNJ11 or ABCC8 variants can move from insulin injections to tablets that encourage their own beta cells to release insulin. By comparison, children with TMEM167A variants currently need insulin alongside comprehensive neurological care, while research investigates cellular stress pathways.

What TMEM167A means for parents and research

For families, this science can seem distant from everyday responsibilities such as managing feeds, checking glucose and attending hospital appointments. Even so, a genetic explanation may provide clarity. It confirms that neither pregnancy nor early parenting caused the condition. It also supplies a defined focus for future clinical trials and a clearer route for relatives seeking to understand their own risk.

For researchers, TMEM167A broadens the conversation around illnesses that involve several organs at the same time. Conditions often approached as isolated, including psychiatric disorders, metabolic syndromes and epilepsy, may have shared early developmental origins in common cellular pathways. The brain–pancreas overlap in MEDS suggests that further cross-organ syndromes could remain undiscovered among small groups of patients worldwide.

Clinicians must now work out how to incorporate rapid genetic testing into standard neonatal care. Sequencing technology becomes less expensive each year, yet healthcare systems continue to debate when it should be used, who should fund it and how families receiving complicated findings should be supported. With its strong genetic basis and serious clinical implications, neonatal diabetes is rapidly becoming a test case for this developing era of precision paediatrics.

For people living with more common types of diabetes, this subject may appear remote. Nevertheless, it makes a wider point: blood glucose disorders can sometimes arise from fundamental problems in cell biology, rather than lifestyle alone. Studying these rare and severe conditions often clarifies mechanisms relevant to milder forms, including how beta cells age and respond to long-term stress. What is learned from a small number of newborns today could shape next-generation treatment for millions of adults tomorrow.