A molecularly defined neural circuit for cold defense revealed by targeted single-nucleus transcriptomic mapping

The neural control of core body temperature homeostasis is fundamental to mammalian survival, yet the mechanisms underlying cold defense are incompletely understood. Cold-activated neurons in the brainstem and hypothalamus are scattered, rare, and their activation persists only shortly. These characteristics have hampered their precise identification and functional dissection. To resolve this, we developed a targeted single-nucleus transcriptomic mapping method – LASAR-seq – to profile sparsely activated neurons by integrating modified FOS immunostaining, laser-capture microdissection, and transcriptomic mapping. This allowed us to identify Grp ⁺ parabrachial neurons as key mediators for cold-defense, encoding dynamic temperature changes and driving multi-modal thermoregulatory responses. Their monosynaptic connection to Gpr101 ⁺ preoptic neurons, which encode absolute temperatures to scale defensive outputs, reveals a dedicated circuit for cold-defense. Our work resolves a long-standing gap in homeostatic neuroscience and establishes LASAR-seq as a powerful tool for linking sparse neural activity to molecular identity and circuit function in complex nervous systems.